Feed-forward control for quantum state protection against decoherence

Wang, Chao-Quan; Xu, Bao-Ming; Zou, Jian; He, Zhi; Yan, Yan; Li, Jungang; Shao, Bin

doi:10.1103/physreva.89.032303

Cited by 45 publications

(37 citation statements)

References 39 publications

(71 reference statements)

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“…This is not the case at least for the amplitude damping noise, e.g. spontaneous emission; it is shown numerically that there exists a quantum protocol that can do better than the "do nothing" and "discriminate & reprepare" protocols [12]. Our result suggests that noise suppression for completely unknown input states is impossible except by using the bias or anisotropy of the noise itself even when one includes the ex-ante control in the scheme.…”

Section: Conclusion and Discussionmentioning

confidence: 87%

Noise suppression by quantum control before and after the noise

2017

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We discuss the possibility of protecting the state of a quantum system that goes through noise, by measurements/operations before and after the noise process. The aim is to seek for the optimal protocol that makes the input and output states as close as possible and clarify the role of the measurements therein. We consider two cases; one can perform quantum measurements/operations (i) only after the noise process and (ii) both before and after that. We prove in the two-dimensional Hilbert space that, in the case (i), the noise suppression is essentially impossible for all types of noise and, in the case (ii), the optimal protocol for the depolarizing noise is either the "do nothing" protocol or the "discriminate & reprepare" protocol. These protocols are not "truly quantum" and can be considered as classical. They involve no measurement or only use the measurement outcomes. These results describe the fundamental limitations in quantum mechanics from the viewpoint of control theory. Finally, we conjecture that a statement similar to the case (ii) holds for higher-dimensional Hilbert spaces and present some numerical evidence.

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Section: Conclusion and Discussionmentioning

confidence: 87%

Noise suppression by quantum control before and after the noise

2017

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“…In addition to the above methods, Sun et al [27] firstly showed that weak measurement together with bit flip can protect the quantum entanglement from amplitude damping. Similarly, Wang et al [28] proposed a feed-forward scheme for protecting quantum state against amplitude damping. But most of the currently existing entanglement reversal (protection) schemes only can slow down the disentanglement, and the complete recovery of entanglement only occurs for the cases where the magnitude of the system decoherence, the strength of the weak measurement, and the strength of the reversing measurement satisfy a specific relation.…”

Section: Introductionmentioning

confidence: 98%

Protecting multipartite entanglement against weak-measurement-induced amplitude damping by local unitary operations

Zong

Yang

et al. 2015

Quantum Inf Process

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Protecting entanglement from decoherence has attracted more and more attention recently. Amplitude damping is a typical decoherence mechanism. If we detect the environment to guarantee no excitation escapes from the system, the amplitude damping is modified into a weak measurement of the system state. In this paper, based on local pulse series, we propose a scheme for protecting tripartite entanglement against decaying caused by weak-measurement-induced damping. Unlike previous bipartite state protection schemes, we consider three different situations: A series of unitary operations are applied on all of the three qubits, on two of the three qubits, and on only one qubit. The results show that this protocol can protect remote tripartite entanglement with a wide range of unitary operations. For the case of GHZ state, when the uniform pulses are applied on all qubits or on two qubits, the tripartite entanglement can be fixed around the entanglement of the initial state. Moreover, in the W state case, if a train of uniform pulses is applied on two qubits, we can see that the bipartite entanglement can be enhanced to the maximum with the third qubit being traced out. We also generalize our scheme to the cases of the superposition and mixture of GHZ and W states, and the numerical simulation shows that our protection scheme still works fine. The most distinct advantage of this entanglement protection scheme is that there is no need for the users to synchronize their operations. The 123 X.-L. Zong et al. fluctuations of the time interval between two adjacent local unitary operations, the operation parameters, and the pulse duration are all taken into consideration. All these advantages suggest that our scheme is much simpler and feasible, which may warrant its experimental realization.

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“…Fortunately, the methods of the active process have been researched, such as quantum error correction codes (from the concept of classical redundancy) 14 – 16 , dynamical decoupling controls (switching to decouple the interaction between the systems and the environment) 17 – 19 , and feedback controls (performing the optimal operation from the measurement result) 20 – 22 .…”

Section: Introductionmentioning

confidence: 99%

Preparation of quantum information encoded on three-photon decoherence-free states via cross-Kerr nonlinearities

Heo

Kang

Hong³

et al. 2018

Sci Rep

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We present a scheme to encode quantum information (single logical qubit information) into three-photon decoherence-free states, which can conserve quantum information from collective decoherence, via nonlinearly optical gates (using cross-Kerr nonlinearities: XKNLs) and linearly optical devices. For the preparation of the decoherence-free state, the nonlinearly optical gates (multi-photon gates) consist of weak XKNLs, quantum bus (qubus) beams, and photon-number-resolving (PNR) measurement. Then, by using a linearly optical device, quantum information can be encoded on three-photon decoherence-free state prepared. Subsequently, by our analysis, we show that the nonlinearly optical gates using XKNLs, qubus beams, and PNR measurement are robust against the decoherence effect (photon loss and dephasing) in optical fibers. Consequently, our scheme can be experimentally implemented to efficiently generate three-photon decoherence-free state encoded quantum information, in practice.

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Feed-forward control for quantum state protection against decoherence

Cited by 45 publications

References 39 publications

Noise suppression by quantum control before and after the noise

Noise suppression by quantum control before and after the noise

Protecting multipartite entanglement against weak-measurement-induced amplitude damping by local unitary operations

Preparation of quantum information encoded on three-photon decoherence-free states via cross-Kerr nonlinearities

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