We study the geometric measure of quantum coherence recently proposed in[Phys.Rev.Lett.115(2015)020403].Both lower and upper bounds of this measure are provided.These bounds are shown to be tight for a class of import...We study the geometric measure of quantum coherence recently proposed in[Phys.Rev.Lett.115(2015)020403].Both lower and upper bounds of this measure are provided.These bounds are shown to be tight for a class of important coherent states—maximally coherent mixed states.The trade-off relation between quantum coherence and mixedness for this measure is also discussed.展开更多
We introduce Quafu-Qcover,an open-source cloud-based software package developed for solving combinatorial optimization problems using quantum simulators and hardware backends.Quafu-Qcover provides a standardized and c...We introduce Quafu-Qcover,an open-source cloud-based software package developed for solving combinatorial optimization problems using quantum simulators and hardware backends.Quafu-Qcover provides a standardized and comprehensive workflow that utilizes the quantum approximate optimization algorithm(QAOA).It facilitates the automatic conversion of the original problem into a quadratic unconstrained binary optimization(QUBO)model and its corresponding Ising model,which can be subsequently transformed into a weight graph.The core of Qcover relies on a graph decomposition-based classical algorithm,which efficiently derives the optimal parameters for the shallow QAOA circuit.Quafu-Qcover incorporates a dedicated compiler capable of translating QAOA circuits into physical quantum circuits that can be executed on Quafu cloud quantum computers.Compared to a general-purpose compiler,our compiler demonstrates the ability to generate shorter circuit depths,while also exhibiting superior speed performance.Additionally,the Qcover compiler has the capability to dynamically create a library of qubits coupling substructures in real-time,utilizing the most recent calibration data from the superconducting quantum devices.This ensures that computational tasks can be assigned to connected physical qubits with the highest fidelity.The Quafu-Qcover allows us to retrieve quantum computing sampling results using a task ID at any time,enabling asynchronous processing.Moreover,it incorporates modules for results preprocessing and visualization,facilitating an intuitive display of solutions for combinatorial optimization problems.We hope that Quafu-Qcover can serve as an instructive illustration for how to explore application problems on the Quafu cloud quantum computers.展开更多
With the rapid advancement of quantum computing,hybrid quantum–classical machine learning has shown numerous potential applications at the current stage,with expectations of being achievable in the noisy intermediate...With the rapid advancement of quantum computing,hybrid quantum–classical machine learning has shown numerous potential applications at the current stage,with expectations of being achievable in the noisy intermediate-scale quantum(NISQ)era.Quantum reinforcement learning,as an indispensable study,has recently demonstrated its ability to solve standard benchmark environments with formally provable theoretical advantages over classical counterparts.However,despite the progress of quantum processors and the emergence of quantum computing clouds,implementing quantum reinforcement learning algorithms utilizing parameterized quantum circuits(PQCs)on NISQ devices remains infrequent.In this work,we take the first step towards executing benchmark quantum reinforcement problems on real devices equipped with at most 136 qubits on the BAQIS Quafu quantum computing cloud.The experimental results demonstrate that the policy agents can successfully accomplish objectives under modified conditions in both the training and inference phases.Moreover,we design hardware-efficient PQC architectures in the quantum model using a multi-objective evolutionary algorithm and develop a learning algorithm that is adaptable to quantum devices.We hope that the Quafu-RL can be a guiding example to show how to realize machine learning tasks by taking advantage of quantum computers on the quantum cloud platform.展开更多
Quantum networks play a pivotal role in the advancement of quantum technologies,expanding the scope of applications and communication distances.However,the absence of practical quantum repeaters poses a significant ob...Quantum networks play a pivotal role in the advancement of quantum technologies,expanding the scope of applications and communication distances.However,the absence of practical quantum repeaters poses a significant obstacle to large-scale network construction.Trusted repeater networks,on the other hand,utilize classical trusted repeaters to connect users,thereby sacrificing the information-theoretic security advantage inherent in quantum communication.In this study,we propose a scheme for constructing a fully quantum network in which any two users are directly connected via a switchable optical router,ensuring information-theoretic security across the entire network with existing technologies.Considering that the practical point-to-point quantum communication distance in optical fibers has reached 100 km,our scheme effectively addresses the challenge of building a fully quantum network within an urban area.A 40-km-long functional quantum network has been established using commercial optical links,enabling full operations of tasks such as quantum secure direct communication and quantum key distribution.展开更多
At present,we are in the noisy-intermediate-scale-quantum era of quantum information science and technology[1],in which there are relatively large numbers of qubits with noise.For instance,the error rate of current su...At present,we are in the noisy-intermediate-scale-quantum era of quantum information science and technology[1],in which there are relatively large numbers of qubits with noise.For instance,the error rate of current superconducting qubits is orders of magnitude away from practical application.To solve this problem,various methods have been used,such as holonomic quantum gate[2],dynamical decoupling[3],entanglement purification[4],and quantum error correction[5].展开更多
Security in communication is vital in modern life. At present, security is realized by an encryption process in cryptography. It is unbelievable if a secure communication is achievable without encryption. In quantum c...Security in communication is vital in modern life. At present, security is realized by an encryption process in cryptography. It is unbelievable if a secure communication is achievable without encryption. In quantum cryptography, there is a unique form of quantum communication, quantum secure direct communication, where secret information is transmitted directly over a quantum channel. Quantum secure direct communication is drastically distinct from our conventional concept of secure communication, because it does not require key distribution, key storage and ciphertext transmission, and eliminates the encryption procedure completely. Hence it avoids in principle all the security loopholes associated with key and ciphertext in traditional secure communications. For practical implementation, defects always exist in real devices and it may downgrade the security. Among the various device imperfections, those with the measurement devices are the most prominent and serious ones. Here we report a measurementdevice-independent quantum secure direct communication protocol using Einstein-Podolsky-Rosen pairs. This protocol eradicates the security vulnerabilities associated with the measurement device,and greatly enhances the practical security of quantum secure direct communication. In addition to the security advantage, this protocol has an extended communication distance, and a high communication capacity.展开更多
Quantum secure direct communication is an important mode of quantum communication in which secret messages are securely communicated directly over a quantum channel.Quantum secure direct communication is also a basic ...Quantum secure direct communication is an important mode of quantum communication in which secret messages are securely communicated directly over a quantum channel.Quantum secure direct communication is also a basic cryptographic primitive for constructing other quantum communication tasks,such as quantum authentication and quantum dialog.Here,we report the first experimental demonstration of quantum secure direct communication based on the DL04 protocol and equipped with single-photon frequency coding that explicitly demonstrated block transmission.In our experiment,we provided 16 different frequency channels,equivalent to a nibble of four-bit binary numbers for direct information transmission.The experiment firmly demonstrated the feasibility of quantum secure direct communication in the presence of noise and loss.展开更多
"Device-independent"not only represents a relaxation of the security assumptions about the internal working of the quantum devices,but also can enhance the security of the quantum communication.In the paper,..."Device-independent"not only represents a relaxation of the security assumptions about the internal working of the quantum devices,but also can enhance the security of the quantum communication.In the paper,we put forward the first device-independent quantum secure direct communication(DIQSDC)protocol and analyze its security and communication efficiency against collective attacks.Under practical noisy quantum channel condition,the photon transmission loss and photon state decoherence would reduce DI-QSDC’s communication quality and threaten its absolute security.For solving the photon transmission loss and decoherence problems,we adopt noiseless linear amplification(NLA)protocol and entanglement purification protocol(EPP)to modify the DI-QSDC protocol.With the help of the NLA and EPP,we can guarantee DI-QSDC’s absolute security and effectively improve its communication quality.展开更多
The security of quantum communication is based on the laws of quantum mechanics,which can resist attacks from any powerful classical and quantum computers.It has great potential in secure communication in the future.O...The security of quantum communication is based on the laws of quantum mechanics,which can resist attacks from any powerful classical and quantum computers.It has great potential in secure communication in the future.One well-known form of quantum communication is quantum key distribution(QKD),where random numbers are transmitted in the quantum channel to generate a shared key between two remote parties.展开更多
Rapid development of supercomputers and the prospect of quantum computers are posing increasingly serious threats to the security of communication.Using the principles of quantum mechanics,quantum communication offers...Rapid development of supercomputers and the prospect of quantum computers are posing increasingly serious threats to the security of communication.Using the principles of quantum mechanics,quantum communication offers provable security of communication and is a promising solution to counter such threats.Quantum secure direct communication(QSDC)is one important branch of quantum communication.In contrast to other branches of quantum communication,it transmits secret information directly.Recently,remarkable progress has been made in proof-of-principle experimental demonstrations of QSDC.However,it remains a technical feat to bring QSDC into a practical application.Here,we report the implementation of a practical quantum secure communication system.The security is analyzed in the Wyner wiretap channel theory.The system uses a coding scheme of concatenation of lowdensity parity-check(LDPC)codes and works in a regime with a realistic environment of high noise and high loss.The present system operates with a repetition rate of 1 MHz at a distance of 1.5 kilometers.The secure communication rate is 50 bps,sufficient to effectively send text messages and reasonably sized files of images and sounds.展开更多
Rapid progress has been made in quantum secure direct communication in recent years.For practical application,it is important to improve the performances,such as the secure information rate and the communication dista...Rapid progress has been made in quantum secure direct communication in recent years.For practical application,it is important to improve the performances,such as the secure information rate and the communication distance.In this paper,we report an elaborate physical system design and protocol with much enhanced performance.This design increased the secrecy capacity greatly by achieving an ultra-low quantum bit error rate of<0.1%,one order of magnitude smaller than that of existing systems.Compared to previous systems,the proposed scheme uses photonic time-bin and phase states,operating at 50 MHz of repetition rate,which can be easily upgraded to over 1 GHz using current on-the-shelf technology.The results of our experimentation demonstrate that the proposed system can tolerate more channel loss,from 5.1 dB,which is about 28.3 km in fiber in the previous scheme,to 18.4 dB,which corresponds to fiber length of 102.2 km.Thus,the experiment shows that intercity quantum secure direct communication through fiber is feasible with present-day technology.展开更多
Quantum secure direct communication provides a direct means of conveying secret information via quantum states among legitimate users.The past two decades have witnessed its great strides both theoretically and experi...Quantum secure direct communication provides a direct means of conveying secret information via quantum states among legitimate users.The past two decades have witnessed its great strides both theoretically and experimentally.However,the security analysis of it still stays in its infant.Some practical problems in this field to be solved urgently,such as detector efficiency mismatch,side-channel effect and source imperfection,are propelling the birth of a more impeccable solution.In this paper,we establish a new framework of the security analysis driven by numerics where all the practical problems may be taken into account naturally.We apply this framework to several variations of the DL04 protocol considering real-world experimental conditions.Also,we propose two optimizing methods to process the numerical part of the framework so as to meet different requirements in practice.With these properties considered,we predict the robust framework would open up a broad avenue of the development in the field.展开更多
Advanced Encryption Standard(AES)is one of the most widely used block ciphers nowadays,and has been established as an encryption standard in 2001.Here we design AES-128 and the sample-AES(S-AES)quantum circuits for de...Advanced Encryption Standard(AES)is one of the most widely used block ciphers nowadays,and has been established as an encryption standard in 2001.Here we design AES-128 and the sample-AES(S-AES)quantum circuits for deciphering.In the quantum circuit of AES-128,we perform an affine transformation for the SubBytes part to solve the problem that the initial state of the output qubits in SubBytes is not the|0⟩⊗8 state.After that,we are able to encode the new round sub-key on the qubits encoding the previous round sub-key,and this improvement reduces the number of qubits used by 224 compared with Langenberg et al.’s implementation.For S-AES,a complete quantum circuit is presented with only 48 qubits,which is already within the reach of existing noisy intermediate-scale quantum computers.展开更多
Quantum secure direct communication(QSDC)attracts much attention for it can transmit secret messages directly without sharing a key.In this article,we propose a one-step QSDC protocol,which only requires to distribute...Quantum secure direct communication(QSDC)attracts much attention for it can transmit secret messages directly without sharing a key.In this article,we propose a one-step QSDC protocol,which only requires to distribute polarization-spatial-mode hyperentanglement for one round.In this QSDC protocol,the eavesdropper cannot obtain any message,so that this protocol is unconditionally secure in principle.This protocol is a two-way quantum communication and has high capacity for it can transmit two bits of secret messages with one pair of hyperentanglement.With entanglement fidelities of both polarization and spatial-mode degrees of freedom being 0.98,the maximal communication distance of this onestep QSDC can reach about 216 km.QSDC can also be used to generate the key.In this regard,the key generation rate is estimated about 2.5 times of that in the entanglement-based QKD with the communication distance of 150 km.With the help of future quantum repeaters,this QSDC protocol can provide unconditionally secure communication over arbitrarily long distance.展开更多
Photons that are entangled or correlated in orbital angular momentum have been extensively used for remote sensing,object identification and imaging.It has recently been demonstrated that intensity fluctuations give r...Photons that are entangled or correlated in orbital angular momentum have been extensively used for remote sensing,object identification and imaging.It has recently been demonstrated that intensity fluctuations give rise to the formation of correlations in the orbital angular momentum components and angular positions of random light.Here we demonstrate that the spatial signatures and phase information of an object with rotational symmetries can be identified using classical orbital angular momentum correlations in random light.The Fourier components imprinted in the digital spiral spectrum of the object,as measured through intensity correlations,unveil its spatial and phase information.Sharing similarities with conventional compressive sensing protocols that exploit sparsity to reduce the number of measurements required to reconstruct a signal,our technique allows sensing of an object with fewer measurements than other schemes that use pixel-by-pixel imaging.One remarkable advantage of our technique is that it does not require the preparation of fragile quantum states of light and operates at both low-and high-light levels.In addition,our technique is robust against environmental noise,a fundamental feature of any realistic scheme for remote sensing.展开更多
Quantum computing is a game-changing technology for global academia,research centers and industries including computational science,mathematics,finance,pharmaceutical,materials science,chemistry and cryptography.Altho...Quantum computing is a game-changing technology for global academia,research centers and industries including computational science,mathematics,finance,pharmaceutical,materials science,chemistry and cryptography.Although it has seen a major boost in the last decade,we are still a long way from reaching the maturity of a full-fledged quantum computer.That said,we will be in the noisy-intermediate scale quantum(NISQ)era for a long time,working on dozens or even thousands of qubits quantum computing systems.An outstanding challenge,then,is to come up with an application that can reliably carry out a nontrivial task of interest on the near-term quantum devices with non-negligible quantum noise.To address this challenge,several near-term quantum computing techniques,including variational quantum algorithms,error mitigation,quantum circuit compilation and benchmarking protocols,have been proposed to characterize and mitigate errors,and to implement algorithms with a certain resistance to noise,so as to enhance the capabilities of near-term quantum devices and explore the boundaries of their ability to realize useful applications.Besides,the development of near-term quantum devices is inseparable from the efficient classical sim-ulation,which plays a vital role in quantum algorithm design and verification,error-tolerant verification and other applications.This review will provide a thorough introduction of these near-term quantum computing techniques,report on their progress,and finally discuss the future prospect of these techniques,which we hope will motivate researchers to undertake additional studies in this field.展开更多
There is a remarkable characteristic of photosynthesis in nature, that is, the energy transfer efficiency is close to 100%. Recently, due to the rapid progress made in the experimental techniques, quantum coherent eff...There is a remarkable characteristic of photosynthesis in nature, that is, the energy transfer efficiency is close to 100%. Recently, due to the rapid progress made in the experimental techniques, quantum coherent effects have been experimentally demonstrated. Traditionally, the incoherent theories are capable of calculating the energy transfer efficiency, e.g.,(generalized) F?rster theory and modified Redfield theory(MRT). However, in order to describe the quantum coherent effects in photosynthesis, one has to exploit coherent theories, such as hierarchical equation of motion(HEOM), quantum path integral, coherent modified Redfield theory(CMRT), small-polaron quantum master equation, and general Bloch-Redfield theory in addition to the Redfield theory. Here, we summarize the main points of the above approaches,which might be beneficial to the quantum simulation of quantum dynamics of exciton energy transfer(EET) in natural photosynthesis, and shed light on the design of artificial light-harvesting devices.展开更多
Efficient quantum circuits for arithmetic operations are vital for quantum algorithms.A fault-tolerant circuit is required for a robust quantum computing in the presence of noise.Quantum circuits based on Clifford+T g...Efficient quantum circuits for arithmetic operations are vital for quantum algorithms.A fault-tolerant circuit is required for a robust quantum computing in the presence of noise.Quantum circuits based on Clifford+T gates are easily rendered faulttolerant.Therefore,reducing the T-depth and T-Count without increasing the qubit number represents vital optimization goals for quantum circuits.In this study,we propose the fault-tolerant implementations for TR and Peres gates with optimized T-depth and T-Count.Next,we design fault-tolerant circuits for quantum arithmetic operations using the TR and Peres gates.Then,we implement cyclic and complete translations of quantum images using quantum arithmetic operations,and the scalar matrix multiplication.Comparative analysis and simulation results reveal that the proposed arithmetic and image operations are efficient.For instance,cyclic translations of a quantum image produce 50%T-depth reduction relative to the previous best-known cyclic translation.展开更多
Opto-thermal relaxation is one of the most important properties of nonlinear optical materials.Rapid and high precision measurement of this parameter is vital in both fundamental research and applications.Current meas...Opto-thermal relaxation is one of the most important properties of nonlinear optical materials.Rapid and high precision measurement of this parameter is vital in both fundamental research and applications.Current measurement uses either complicated structure with poor precision or high power heating source with low efficiency.Here,we propose a pump-probe method(PPM) to optically measure the thermal relaxation using whispering gallery mode(WGM) microcavities.When the pump laser shines on a microcavity,the materials absorb the input power resonantly and heat up.Then the heat dissipates from the cavities to the surroundings.The opto-thermal effect induces a refractive index change reflected in the signal light transmission spectra.By analyzing the curve character of the transmission spectra of the signal response in the spontaneous relaxation process,the thermal relaxation time can be rapidly measured with high precision.Additionally,we systematically verify the PPM using microtoroids under various pump powers and at various locking points of the signal laser mode.The small rate of refractive index changes($10à8) can be discerned with an input pump power as low as 11.816 l W.Hence,the PPM can be used to detect refractive index perturbation,like gas or liquid sensing,temperature fluctuations with ultra-high sensitivity and be applied to optical materials analysis efficiently.展开更多
Based on the dispersive interaction between a high quality factor microcavity and nano-objects,whisperinggallery-mode microcavities have been widely used in highly sensitive sensing.Here,we propose a novel method to e...Based on the dispersive interaction between a high quality factor microcavity and nano-objects,whisperinggallery-mode microcavities have been widely used in highly sensitive sensing.Here,we propose a novel method to enhance the sensitivity of the optical frequency shift and reduce the impact of the laser frequency noise on the detection resolution through Brillouin cavity optomechanics in a parity-time symmetric system.The optical spring effect is sensitive to the perturbation of optical modes around the exceptional point.By monitoring the shift of the mechanical frequency,the detection sensitivity for the optical frequency shift is enhanced by 2 orders of magnitude compared with conventional approaches.We find the optical spring effect is robust to the laser frequency noise around the exceptional point,which can reduce the detection limitation caused by the laser frequency instability.Thus,our method can improve the sensing ability for nano-object sensing and other techniques based on the frequency shift of the optical mode.展开更多
基金Supported by the National Basic Research Program of China under Grant No.2015CB921002the National Natural Science Foundation of China under Grant Nos.11175094,91221205,11275131+2 种基金Fundamental Research Funds for the Central Universities under Grant No.16CX02049Athe Shandong Provincial Natural Science Foundation under Grant No.ZR2016AQ06the Postdoctor Science Foundation under Grant No.2016M600997
文摘We study the geometric measure of quantum coherence recently proposed in[Phys.Rev.Lett.115(2015)020403].Both lower and upper bounds of this measure are provided.These bounds are shown to be tight for a class of important coherent states—maximally coherent mixed states.The trade-off relation between quantum coherence and mixedness for this measure is also discussed.
基金supported by the National Natural Science Foundation of China(Grant No.92365206)the support of the China Postdoctoral Science Foundation(Certificate Number:2023M740272)+1 种基金supported by the National Natural Science Foundation of China(Grant No.12247168)China Postdoctoral Science Foundation(Certificate Number:2022TQ0036)。
文摘We introduce Quafu-Qcover,an open-source cloud-based software package developed for solving combinatorial optimization problems using quantum simulators and hardware backends.Quafu-Qcover provides a standardized and comprehensive workflow that utilizes the quantum approximate optimization algorithm(QAOA).It facilitates the automatic conversion of the original problem into a quadratic unconstrained binary optimization(QUBO)model and its corresponding Ising model,which can be subsequently transformed into a weight graph.The core of Qcover relies on a graph decomposition-based classical algorithm,which efficiently derives the optimal parameters for the shallow QAOA circuit.Quafu-Qcover incorporates a dedicated compiler capable of translating QAOA circuits into physical quantum circuits that can be executed on Quafu cloud quantum computers.Compared to a general-purpose compiler,our compiler demonstrates the ability to generate shorter circuit depths,while also exhibiting superior speed performance.Additionally,the Qcover compiler has the capability to dynamically create a library of qubits coupling substructures in real-time,utilizing the most recent calibration data from the superconducting quantum devices.This ensures that computational tasks can be assigned to connected physical qubits with the highest fidelity.The Quafu-Qcover allows us to retrieve quantum computing sampling results using a task ID at any time,enabling asynchronous processing.Moreover,it incorporates modules for results preprocessing and visualization,facilitating an intuitive display of solutions for combinatorial optimization problems.We hope that Quafu-Qcover can serve as an instructive illustration for how to explore application problems on the Quafu cloud quantum computers.
基金supported by the Beijing Academy of Quantum Information Sciencessupported by the National Natural Science Foundation of China(Grant No.92365206)+2 种基金the support of the China Postdoctoral Science Foundation(Certificate Number:2023M740272)supported by the National Natural Science Foundation of China(Grant No.12247168)China Postdoctoral Science Foundation(Certificate Number:2022TQ0036)。
文摘With the rapid advancement of quantum computing,hybrid quantum–classical machine learning has shown numerous potential applications at the current stage,with expectations of being achievable in the noisy intermediate-scale quantum(NISQ)era.Quantum reinforcement learning,as an indispensable study,has recently demonstrated its ability to solve standard benchmark environments with formally provable theoretical advantages over classical counterparts.However,despite the progress of quantum processors and the emergence of quantum computing clouds,implementing quantum reinforcement learning algorithms utilizing parameterized quantum circuits(PQCs)on NISQ devices remains infrequent.In this work,we take the first step towards executing benchmark quantum reinforcement problems on real devices equipped with at most 136 qubits on the BAQIS Quafu quantum computing cloud.The experimental results demonstrate that the policy agents can successfully accomplish objectives under modified conditions in both the training and inference phases.Moreover,we design hardware-efficient PQC architectures in the quantum model using a multi-objective evolutionary algorithm and develop a learning algorithm that is adaptable to quantum devices.We hope that the Quafu-RL can be a guiding example to show how to realize machine learning tasks by taking advantage of quantum computers on the quantum cloud platform.
基金funded by the National Natural Science Foundation of China(Grant No.62471046)funded by the National Natural Science Foundation of China(Grant No.12204051)+3 种基金funded by the National Natural Science Foundation of China(Grant Nos.62501057,62131002)the National Natural Science Foundation of China(Grant No.12205011)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2022QNRC001)funded by the Young Elite Scientists Sponsorship Program by CAST(Grant No.YESS20240786)。
文摘Quantum networks play a pivotal role in the advancement of quantum technologies,expanding the scope of applications and communication distances.However,the absence of practical quantum repeaters poses a significant obstacle to large-scale network construction.Trusted repeater networks,on the other hand,utilize classical trusted repeaters to connect users,thereby sacrificing the information-theoretic security advantage inherent in quantum communication.In this study,we propose a scheme for constructing a fully quantum network in which any two users are directly connected via a switchable optical router,ensuring information-theoretic security across the entire network with existing technologies.Considering that the practical point-to-point quantum communication distance in optical fibers has reached 100 km,our scheme effectively addresses the challenge of building a fully quantum network within an urban area.A 40-km-long functional quantum network has been established using commercial optical links,enabling full operations of tasks such as quantum secure direct communication and quantum key distribution.
文摘At present,we are in the noisy-intermediate-scale-quantum era of quantum information science and technology[1],in which there are relatively large numbers of qubits with noise.For instance,the error rate of current superconducting qubits is orders of magnitude away from practical application.To solve this problem,various methods have been used,such as holonomic quantum gate[2],dynamical decoupling[3],entanglement purification[4],and quantum error correction[5].
基金supported by the National Basic Research Program of China(2017YFA0303700 and 2015CB921001)the National Natural Science Foundation of China(61726801,11474168 and 11474181)the Beijing Advanced Innovation Center for Future Chip(ICFC)
文摘Security in communication is vital in modern life. At present, security is realized by an encryption process in cryptography. It is unbelievable if a secure communication is achievable without encryption. In quantum cryptography, there is a unique form of quantum communication, quantum secure direct communication, where secret information is transmitted directly over a quantum channel. Quantum secure direct communication is drastically distinct from our conventional concept of secure communication, because it does not require key distribution, key storage and ciphertext transmission, and eliminates the encryption procedure completely. Hence it avoids in principle all the security loopholes associated with key and ciphertext in traditional secure communications. For practical implementation, defects always exist in real devices and it may downgrade the security. Among the various device imperfections, those with the measurement devices are the most prominent and serious ones. Here we report a measurementdevice-independent quantum secure direct communication protocol using Einstein-Podolsky-Rosen pairs. This protocol eradicates the security vulnerabilities associated with the measurement device,and greatly enhances the practical security of quantum secure direct communication. In addition to the security advantage, this protocol has an extended communication distance, and a high communication capacity.
基金sponsored by the 973 Program(No.2012CB921603)863 Program(No.2011AA010801)+3 种基金the Natural Science Foundation of China(Nos.61527824,11374196,10934004 and 11204166)PCSIRT(No.IRT 13076)supported by the Natural Science Foundation of China(Nos.11175094 and 91221205)the National Basic Research Program of China(No.2015CB921001).
文摘Quantum secure direct communication is an important mode of quantum communication in which secret messages are securely communicated directly over a quantum channel.Quantum secure direct communication is also a basic cryptographic primitive for constructing other quantum communication tasks,such as quantum authentication and quantum dialog.Here,we report the first experimental demonstration of quantum secure direct communication based on the DL04 protocol and equipped with single-photon frequency coding that explicitly demonstrated block transmission.In our experiment,we provided 16 different frequency channels,equivalent to a nibble of four-bit binary numbers for direct information transmission.The experiment firmly demonstrated the feasibility of quantum secure direct communication in the presence of noise and loss.
基金supported by the National Natural Science Foundation of China (11974189 and 11974205)the China Postdoctoral Science Foundation (2018M642293)+1 种基金the Open Research Fund of the Key Lab of Broadband Wireless Communication and Sensor Network Technology,Nanjing University of Posts and Telecommunications, Ministry of Education (JZNY201908)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘"Device-independent"not only represents a relaxation of the security assumptions about the internal working of the quantum devices,but also can enhance the security of the quantum communication.In the paper,we put forward the first device-independent quantum secure direct communication(DIQSDC)protocol and analyze its security and communication efficiency against collective attacks.Under practical noisy quantum channel condition,the photon transmission loss and photon state decoherence would reduce DI-QSDC’s communication quality and threaten its absolute security.For solving the photon transmission loss and decoherence problems,we adopt noiseless linear amplification(NLA)protocol and entanglement purification protocol(EPP)to modify the DI-QSDC protocol.With the help of the NLA and EPP,we can guarantee DI-QSDC’s absolute security and effectively improve its communication quality.
基金supported by the Key-Area Research and Development Program of Guangdong Province (2018B030325002)National Key Research and Development Program of China (2017YFA0303700)+2 种基金the National Natural Science Foundation of China (11974205)Beijing Advanced Innovation Center for Future Chip (ICFC)Tsinghua University Initiative Scientific Research Program
文摘The security of quantum communication is based on the laws of quantum mechanics,which can resist attacks from any powerful classical and quantum computers.It has great potential in secure communication in the future.One well-known form of quantum communication is quantum key distribution(QKD),where random numbers are transmitted in the quantum channel to generate a shared key between two remote parties.
基金supported by the National Basic Research Program of China under Grant Nos.2017YFA0303700 and 2015CB921001the National Natural Science Foundation of China under Grant Nos.61727801,11474181,61871257,and 11774197supported in part by the Beijing Advanced Innovation Center for Future Chip(ICFC).
文摘Rapid development of supercomputers and the prospect of quantum computers are posing increasingly serious threats to the security of communication.Using the principles of quantum mechanics,quantum communication offers provable security of communication and is a promising solution to counter such threats.Quantum secure direct communication(QSDC)is one important branch of quantum communication.In contrast to other branches of quantum communication,it transmits secret information directly.Recently,remarkable progress has been made in proof-of-principle experimental demonstrations of QSDC.However,it remains a technical feat to bring QSDC into a practical application.Here,we report the implementation of a practical quantum secure communication system.The security is analyzed in the Wyner wiretap channel theory.The system uses a coding scheme of concatenation of lowdensity parity-check(LDPC)codes and works in a regime with a realistic environment of high noise and high loss.The present system operates with a repetition rate of 1 MHz at a distance of 1.5 kilometers.The secure communication rate is 50 bps,sufficient to effectively send text messages and reasonably sized files of images and sounds.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.62025110,61871257,11974205 and 11474181)by the NSAF(Grant No.U1530117)+4 种基金by the National Key R&D Program of China(Grant No.2017YFA0303700)by the National Basic Research Program of China(Grant No.2015CB921001)by the Key-Area Research and Development Program of Guangdong province(2018B030325002)by the Tsinghua University Initiative Scientific Research Programby the Beijing Innovation Center for Future Chips(ICFC).
文摘Rapid progress has been made in quantum secure direct communication in recent years.For practical application,it is important to improve the performances,such as the secure information rate and the communication distance.In this paper,we report an elaborate physical system design and protocol with much enhanced performance.This design increased the secrecy capacity greatly by achieving an ultra-low quantum bit error rate of<0.1%,one order of magnitude smaller than that of existing systems.Compared to previous systems,the proposed scheme uses photonic time-bin and phase states,operating at 50 MHz of repetition rate,which can be easily upgraded to over 1 GHz using current on-the-shelf technology.The results of our experimentation demonstrate that the proposed system can tolerate more channel loss,from 5.1 dB,which is about 28.3 km in fiber in the previous scheme,to 18.4 dB,which corresponds to fiber length of 102.2 km.Thus,the experiment shows that intercity quantum secure direct communication through fiber is feasible with present-day technology.
基金This work was supported by the National Key Research and Development Program of China under Grant No.2017YFA0303700the Key Research and Development Program of Guangdong province under Grant No.2018B030325002+1 种基金the National Natural Science Foundation of China under Grant No.11974205Beijing Advanced Innovation Center for Future Chip(ICFC).
文摘Quantum secure direct communication provides a direct means of conveying secret information via quantum states among legitimate users.The past two decades have witnessed its great strides both theoretically and experimentally.However,the security analysis of it still stays in its infant.Some practical problems in this field to be solved urgently,such as detector efficiency mismatch,side-channel effect and source imperfection,are propelling the birth of a more impeccable solution.In this paper,we establish a new framework of the security analysis driven by numerics where all the practical problems may be taken into account naturally.We apply this framework to several variations of the DL04 protocol considering real-world experimental conditions.Also,we propose two optimizing methods to process the numerical part of the framework so as to meet different requirements in practice.With these properties considered,we predict the robust framework would open up a broad avenue of the development in the field.
基金support from the National Natural Science Foundation of China under Grant Nos.11974205 and 11774197,the National Key Research and Development Program of China(No.2017YFA0303700)the Key Research and Development Program of Guangdong province(No.2018B030325002)+1 种基金and Beijing Advanced Innovation Center for Future Chip(ICFC).S.W.also acknowledges the China Postdoctoral Science Foundation(No.2020M670172)the National Natural Science Foundation of China under Grant No.12005015.
文摘Advanced Encryption Standard(AES)is one of the most widely used block ciphers nowadays,and has been established as an encryption standard in 2001.Here we design AES-128 and the sample-AES(S-AES)quantum circuits for deciphering.In the quantum circuit of AES-128,we perform an affine transformation for the SubBytes part to solve the problem that the initial state of the output qubits in SubBytes is not the|0⟩⊗8 state.After that,we are able to encode the new round sub-key on the qubits encoding the previous round sub-key,and this improvement reduces the number of qubits used by 224 compared with Langenberg et al.’s implementation.For S-AES,a complete quantum circuit is presented with only 48 qubits,which is already within the reach of existing noisy intermediate-scale quantum computers.
基金supported by the National Natural Science Foundation of China(11974189,11974205,and 12175106)the Key Area Research and Development Program of Guangdong Province(2018B030325002)the National Key Research and Development Program of China(2017YFA0303700)。
文摘Quantum secure direct communication(QSDC)attracts much attention for it can transmit secret messages directly without sharing a key.In this article,we propose a one-step QSDC protocol,which only requires to distribute polarization-spatial-mode hyperentanglement for one round.In this QSDC protocol,the eavesdropper cannot obtain any message,so that this protocol is unconditionally secure in principle.This protocol is a two-way quantum communication and has high capacity for it can transmit two bits of secret messages with one pair of hyperentanglement.With entanglement fidelities of both polarization and spatial-mode degrees of freedom being 0.98,the maximal communication distance of this onestep QSDC can reach about 216 km.QSDC can also be used to generate the key.In this regard,the key generation rate is estimated about 2.5 times of that in the entanglement-based QKD with the communication distance of 150 km.With the help of future quantum repeaters,this QSDC protocol can provide unconditionally secure communication over arbitrarily long distance.
基金support from the program of the China Scholarship Council(no.201506210145)the support from the National Natural Science Foundation of China,no.11504337+1 种基金the partial support from the Natural Science Foundation of China under Grant nos 11175094 and 91221205the National Basic Research Program of China under Grant no.2015CB921002。
文摘Photons that are entangled or correlated in orbital angular momentum have been extensively used for remote sensing,object identification and imaging.It has recently been demonstrated that intensity fluctuations give rise to the formation of correlations in the orbital angular momentum components and angular positions of random light.Here we demonstrate that the spatial signatures and phase information of an object with rotational symmetries can be identified using classical orbital angular momentum correlations in random light.The Fourier components imprinted in the digital spiral spectrum of the object,as measured through intensity correlations,unveil its spatial and phase information.Sharing similarities with conventional compressive sensing protocols that exploit sparsity to reduce the number of measurements required to reconstruct a signal,our technique allows sensing of an object with fewer measurements than other schemes that use pixel-by-pixel imaging.One remarkable advantage of our technique is that it does not require the preparation of fragile quantum states of light and operates at both low-and high-light levels.In addition,our technique is robust against environmental noise,a fundamental feature of any realistic scheme for remote sensing.
基金support from the Youth Talent Lifting Project(Grant No.2020-JCJQ-QT-030)the National Natural Science Foundation of China(Grant Nos.11905294,and 12274464)+7 种基金the China Postdoctoral Science Foundation,and the Open Research Fund from State Key Laboratory of High Performance Computing of China(Grant No.201901-01)support from the National Natural Science Foundation of China(Grant Nos.11805279,12074117,61833010,and 12061131011)support from the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the National Natural Science Foundation of China(Grant Nos.61832003,61872334,and 61801459)the National Natural Science Foundation of China(Grant No.12005015)the National Natural Science Foundation of China(Grant Nos.11974205,and 11774197)the National Key Research and Development Program of China(Grant No.2017YFA0303700)the Key Research and Development Program of Guangdong Province(Grant No.2018B030325002).
文摘Quantum computing is a game-changing technology for global academia,research centers and industries including computational science,mathematics,finance,pharmaceutical,materials science,chemistry and cryptography.Although it has seen a major boost in the last decade,we are still a long way from reaching the maturity of a full-fledged quantum computer.That said,we will be in the noisy-intermediate scale quantum(NISQ)era for a long time,working on dozens or even thousands of qubits quantum computing systems.An outstanding challenge,then,is to come up with an application that can reliably carry out a nontrivial task of interest on the near-term quantum devices with non-negligible quantum noise.To address this challenge,several near-term quantum computing techniques,including variational quantum algorithms,error mitigation,quantum circuit compilation and benchmarking protocols,have been proposed to characterize and mitigate errors,and to implement algorithms with a certain resistance to noise,so as to enhance the capabilities of near-term quantum devices and explore the boundaries of their ability to realize useful applications.Besides,the development of near-term quantum devices is inseparable from the efficient classical sim-ulation,which plays a vital role in quantum algorithm design and verification,error-tolerant verification and other applications.This review will provide a thorough introduction of these near-term quantum computing techniques,report on their progress,and finally discuss the future prospect of these techniques,which we hope will motivate researchers to undertake additional studies in this field.
基金supported by the National Basic Research Program of China (2017YFA0303704)the National Natural Science Foundation of China (61727801, 11774197, 11474181, 11674033, 11505007 and 11474026).
文摘There is a remarkable characteristic of photosynthesis in nature, that is, the energy transfer efficiency is close to 100%. Recently, due to the rapid progress made in the experimental techniques, quantum coherent effects have been experimentally demonstrated. Traditionally, the incoherent theories are capable of calculating the energy transfer efficiency, e.g.,(generalized) F?rster theory and modified Redfield theory(MRT). However, in order to describe the quantum coherent effects in photosynthesis, one has to exploit coherent theories, such as hierarchical equation of motion(HEOM), quantum path integral, coherent modified Redfield theory(CMRT), small-polaron quantum master equation, and general Bloch-Redfield theory in addition to the Redfield theory. Here, we summarize the main points of the above approaches,which might be beneficial to the quantum simulation of quantum dynamics of exciton energy transfer(EET) in natural photosynthesis, and shed light on the design of artificial light-harvesting devices.
基金supported by the National Natural Science Foundation of China(Grant Nos.61762012,and 61763014)the Science and Technology Project of Guangxi(Grant No.2018JJA170083)+3 种基金the National Key Research and Development Plan(Grant Nos.2018YFC1200200,and 2018YFC1200205)the Fund for Distinguished Young Scholars of Jiangxi Province(Grant No.2018ACB2101)the Natural Science Foundation of Jiangxi Province of China(Grant No.20192BAB207014)the Science and Technology Research Project of Jiangxi Provincial Education Department(Grant No.GJJ190297)。
文摘Efficient quantum circuits for arithmetic operations are vital for quantum algorithms.A fault-tolerant circuit is required for a robust quantum computing in the presence of noise.Quantum circuits based on Clifford+T gates are easily rendered faulttolerant.Therefore,reducing the T-depth and T-Count without increasing the qubit number represents vital optimization goals for quantum circuits.In this study,we propose the fault-tolerant implementations for TR and Peres gates with optimized T-depth and T-Count.Next,we design fault-tolerant circuits for quantum arithmetic operations using the TR and Peres gates.Then,we implement cyclic and complete translations of quantum images using quantum arithmetic operations,and the scalar matrix multiplication.Comparative analysis and simulation results reveal that the proposed arithmetic and image operations are efficient.For instance,cyclic translations of a quantum image produce 50%T-depth reduction relative to the previous best-known cyclic translation.
基金supported by the National Natural Science Foundation of China(11175094)the National Basic Research Program of China(2015CB921002)
文摘Opto-thermal relaxation is one of the most important properties of nonlinear optical materials.Rapid and high precision measurement of this parameter is vital in both fundamental research and applications.Current measurement uses either complicated structure with poor precision or high power heating source with low efficiency.Here,we propose a pump-probe method(PPM) to optically measure the thermal relaxation using whispering gallery mode(WGM) microcavities.When the pump laser shines on a microcavity,the materials absorb the input power resonantly and heat up.Then the heat dissipates from the cavities to the surroundings.The opto-thermal effect induces a refractive index change reflected in the signal light transmission spectra.By analyzing the curve character of the transmission spectra of the signal response in the spontaneous relaxation process,the thermal relaxation time can be rapidly measured with high precision.Additionally,we systematically verify the PPM using microtoroids under various pump powers and at various locking points of the signal laser mode.The small rate of refractive index changes($10à8) can be discerned with an input pump power as low as 11.816 l W.Hence,the PPM can be used to detect refractive index perturbation,like gas or liquid sensing,temperature fluctuations with ultra-high sensitivity and be applied to optical materials analysis efficiently.
基金National Natural Science Foundation of China(20171311628)Ministry of Science and Technology of the People’s Republic of China(2017YFA0303700)Beijing Advanced Innovation Center for Future Chip
文摘Based on the dispersive interaction between a high quality factor microcavity and nano-objects,whisperinggallery-mode microcavities have been widely used in highly sensitive sensing.Here,we propose a novel method to enhance the sensitivity of the optical frequency shift and reduce the impact of the laser frequency noise on the detection resolution through Brillouin cavity optomechanics in a parity-time symmetric system.The optical spring effect is sensitive to the perturbation of optical modes around the exceptional point.By monitoring the shift of the mechanical frequency,the detection sensitivity for the optical frequency shift is enhanced by 2 orders of magnitude compared with conventional approaches.We find the optical spring effect is robust to the laser frequency noise around the exceptional point,which can reduce the detection limitation caused by the laser frequency instability.Thus,our method can improve the sensing ability for nano-object sensing and other techniques based on the frequency shift of the optical mode.
