Considering two atomic qubits initially in Bell states, we send one qubit into a vacuum cavity with two-photon resonance and leave the other one outside. Using quantum information entropy squeezing theory, the time ev...Considering two atomic qubits initially in Bell states, we send one qubit into a vacuum cavity with two-photon resonance and leave the other one outside. Using quantum information entropy squeezing theory, the time evolutions of the entropy squeezing factor of the atomic qubit inside the cavity are discussed for two cases, i.e., before and after rotation and measurement of the atomic qubit outside the cavity. It is shown that the atomic qubit inside the cavity has no entropy squeezing phenomenon and is always in a decoherent state before the operating atomic qubit outside the cavity. However,the periodical entropy squeezing phenomenon emerges and the optimal entropy squeezing state can be prepared for the atomic qubit inside the cavity by adjusting the rotation angle, choosing the interaction time between the atomic qubit and the cavity, controlling the probability amplitudes of subsystem states. Its physical essence is cutting the entanglement between the atomic qubit and its environment, causing the atomic qubit inside the cavity to change from the initial decoherent state into maximum coherent superposition state, which is a possible way of recovering the coherence of a single atomic qubit in the noise environment.展开更多
To implement generalized quantum measurement （GQM） one has to extend the original Hilbert space. Generally speaking, the additional dimensions of the ancilla space increase as the number of the operators of the GQM ...To implement generalized quantum measurement （GQM） one has to extend the original Hilbert space. Generally speaking, the additional dimensions of the ancilla space increase as the number of the operators of the GQM n increases. This paper presents a scheme for deterministically implementing all possible n-operator CQMs on a single atomic qubit by using only one 2-dimensional ancillary atomic qubit repeatedly, which remarkably reduces the complexity of the realistic physical system. Here the qubit is encoded in the internal states of an atom trapped in an optical cavity and single-photon pulses are employed to provide the interaction between qubits. It shows that the scheme can be performed remotely, and thus it is suitable for implementing CQM in a quantum network. What is more, the number of the total ancilla dimensions in our scheme achieves the theoretic low bound.展开更多
By means of cavity-assisted photon interference, a simple scheme is proposed to implement a symmetric economical phase-covariant quantum cloning machine of two remote qubits, with each in a separate cavity. With our p...By means of cavity-assisted photon interference, a simple scheme is proposed to implement a symmetric economical phase-covariant quantum cloning machine of two remote qubits, with each in a separate cavity. With our present scheme, a high-fidelity cloning machine is realized. Our scheme may be quite useful in terms of distributed quantum information processing.展开更多
We propose two effective schemes for local and remote unknown atomic state comparisons with a cavity-assisted single photon input--output process without any initial entanglement or auxiliary resource. The unambiguous...We propose two effective schemes for local and remote unknown atomic state comparisons with a cavity-assisted single photon input--output process without any initial entanglement or auxiliary resource. The unambiguous state discrim- ination is considered using the state comparison process as the basic module. All the implementation schemes here just involve common quantum logic gates and the single qubit measurement. The analysis shows that our schemes are feasible under the current experimental conditions.展开更多
The cold atom qubit platform emerges as an attractive choice for the next stage of quantum computation research,where a special family of synthetic analytical pulses has considerably improved the experimental performa...The cold atom qubit platform emerges as an attractive choice for the next stage of quantum computation research,where a special family of synthetic analytical pulses has considerably improved the experimental performance of Controlled-PHASE Rydberg blockade gates in recent studies.The success of Controlled-PHASE Rydberg blockade gates triggers the intriguing question of whether the two-qubit Rydberg blockade gate SWAP gate exists.Via investigating the transition linkage structure,we provide a definitive answer to this question and establish the method of fast SWAP Rydberg blockade gates with synthetic continuously modulated driving.These gate protocols use careful analysis to properly generate coherent population transfer and phase accumulation of the wave function in the atom-laser interaction process.They can adapt to finite Rydberg blockade strengths and bear considerable resistance to some major adverse effects such as laser fluctuations.Further examinations reveal that we can anticipate satisfying performances of the method with currently available experimental techniques in relevant research areas.展开更多
Connectivity of two-qubit logic gates plays a crucial and indispensable role in quantum computation research.For the cold atom qubit platform,while the two-qubit Rydberg blockade gate has recently made rapid experimen...Connectivity of two-qubit logic gates plays a crucial and indispensable role in quantum computation research.For the cold atom qubit platform,while the two-qubit Rydberg blockade gate has recently made rapid experimental progress,a pressing challenge is to improve connectivity in pursuit of genuine scalability without sacrificing speed or fidelity.A significant advancement in this direction can be achieved by introducing an extra buffer atom to extend the two-qubit gate beyond purely nearest-neighbor two-body interactions.The buffer atom couples with the two qubit atoms through nearest-neighbor interactions,even though the qubit atoms do not directly exert any physical influence on each other.The established method of off-resonant modulated driving(ORMD)is not only convenient but also lays the groundwork for this latest development.Although the atomic linkage structure here exhibits more complex interactions compared to previous two-body systems,the population can satisfactorily return to the ground state after the ground-Rydberg transition with a properly designed modulation waveform.This can be achieved through one-photon and two-photon ground-Rydberg transitions in common practices.Furthermore,with buffer atom relay or similar structures,it is possible to realize a two-qubit entangling gate between two distant qubit atoms.In addition to demonstrating that such solutions are feasible,the representative modulation patterns are analyzed,showcasing the versatility of buffer-atom-mediated two-qubit gates.From a broader perspective,these efforts enhance the resemblance between the cold atom qubit platform and the superconducting qubit system,with the buffer atom functioning like wires and junctions.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11374096 and 11405052)
文摘Considering two atomic qubits initially in Bell states, we send one qubit into a vacuum cavity with two-photon resonance and leave the other one outside. Using quantum information entropy squeezing theory, the time evolutions of the entropy squeezing factor of the atomic qubit inside the cavity are discussed for two cases, i.e., before and after rotation and measurement of the atomic qubit outside the cavity. It is shown that the atomic qubit inside the cavity has no entropy squeezing phenomenon and is always in a decoherent state before the operating atomic qubit outside the cavity. However,the periodical entropy squeezing phenomenon emerges and the optimal entropy squeezing state can be prepared for the atomic qubit inside the cavity by adjusting the rotation angle, choosing the interaction time between the atomic qubit and the cavity, controlling the probability amplitudes of subsystem states. Its physical essence is cutting the entanglement between the atomic qubit and its environment, causing the atomic qubit inside the cavity to change from the initial decoherent state into maximum coherent superposition state, which is a possible way of recovering the coherence of a single atomic qubit in the noise environment.
基金supported by the National Natural Science Foundation of China (Grant No 10774192)the Fund of Innovation of the Graduate School of National University of Defense Technology (Grant No B080201)
文摘To implement generalized quantum measurement （GQM） one has to extend the original Hilbert space. Generally speaking, the additional dimensions of the ancilla space increase as the number of the operators of the GQM n increases. This paper presents a scheme for deterministically implementing all possible n-operator CQMs on a single atomic qubit by using only one 2-dimensional ancillary atomic qubit repeatedly, which remarkably reduces the complexity of the realistic physical system. Here the qubit is encoded in the internal states of an atom trapped in an optical cavity and single-photon pulses are employed to provide the interaction between qubits. It shows that the scheme can be performed remotely, and thus it is suitable for implementing CQM in a quantum network. What is more, the number of the total ancilla dimensions in our scheme achieves the theoretic low bound.
文摘By means of cavity-assisted photon interference, a simple scheme is proposed to implement a symmetric economical phase-covariant quantum cloning machine of two remote qubits, with each in a separate cavity. With our present scheme, a high-fidelity cloning machine is realized. Our scheme may be quite useful in terms of distributed quantum information processing.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61068001 and 11264042)the China Postdoctoral Science Foundation(Grant No. 2012M520612)the Talent Program of Yanbian University of China (Grant No. 950010001)
文摘We propose two effective schemes for local and remote unknown atomic state comparisons with a cavity-assisted single photon input--output process without any initial entanglement or auxiliary resource. The unambiguous state discrim- ination is considered using the state comparison process as the basic module. All the implementation schemes here just involve common quantum logic gates and the single qubit measurement. The analysis shows that our schemes are feasible under the current experimental conditions.
基金Science and Technology Commission of Shanghai Municipality(24DP2600202)National Key Research and Development Program of China(2024YFB4504002)National Natural Science Foundation of China(92165107)。
文摘The cold atom qubit platform emerges as an attractive choice for the next stage of quantum computation research,where a special family of synthetic analytical pulses has considerably improved the experimental performance of Controlled-PHASE Rydberg blockade gates in recent studies.The success of Controlled-PHASE Rydberg blockade gates triggers the intriguing question of whether the two-qubit Rydberg blockade gate SWAP gate exists.Via investigating the transition linkage structure,we provide a definitive answer to this question and establish the method of fast SWAP Rydberg blockade gates with synthetic continuously modulated driving.These gate protocols use careful analysis to properly generate coherent population transfer and phase accumulation of the wave function in the atom-laser interaction process.They can adapt to finite Rydberg blockade strengths and bear considerable resistance to some major adverse effects such as laser fluctuations.Further examinations reveal that we can anticipate satisfying performances of the method with currently available experimental techniques in relevant research areas.
基金supported by the National Natural Science Foundation of China(Grant Nos.92165107,and 12074391)the Fundamental Research Program of the Chinese Academy of Sciencesthe Science and Technology Commission of Shanghai Municipality。
文摘Connectivity of two-qubit logic gates plays a crucial and indispensable role in quantum computation research.For the cold atom qubit platform,while the two-qubit Rydberg blockade gate has recently made rapid experimental progress,a pressing challenge is to improve connectivity in pursuit of genuine scalability without sacrificing speed or fidelity.A significant advancement in this direction can be achieved by introducing an extra buffer atom to extend the two-qubit gate beyond purely nearest-neighbor two-body interactions.The buffer atom couples with the two qubit atoms through nearest-neighbor interactions,even though the qubit atoms do not directly exert any physical influence on each other.The established method of off-resonant modulated driving(ORMD)is not only convenient but also lays the groundwork for this latest development.Although the atomic linkage structure here exhibits more complex interactions compared to previous two-body systems,the population can satisfactorily return to the ground state after the ground-Rydberg transition with a properly designed modulation waveform.This can be achieved through one-photon and two-photon ground-Rydberg transitions in common practices.Furthermore,with buffer atom relay or similar structures,it is possible to realize a two-qubit entangling gate between two distant qubit atoms.In addition to demonstrating that such solutions are feasible,the representative modulation patterns are analyzed,showcasing the versatility of buffer-atom-mediated two-qubit gates.From a broader perspective,these efforts enhance the resemblance between the cold atom qubit platform and the superconducting qubit system,with the buffer atom functioning like wires and junctions.
