arXiv subjects

Peng Xue

Publications and source records attributed to Peng Xue.

At least 91 records · Page 5Linked to original sources

arXiv2014

Experimental realization of a single qubit SIC POVM on via a one-dimensional photonic quantum walk

Symmetric informationally complete positive operator-valued measurement (SIC-POVM) is one important class of quantum measurement which is crucial for various quantum information processing tasks. SIC-POVMs have the advantage of providing an unbiased estimator for quantum states with the minimal number of outcomes needed for full tomography. We present an experimental approach on a photonic quantum walk which can be used to implement SIC-POVMs on a single-qbubit. The projection measurements of single-photons' positions correspond to elements of SIC-POVM on the polarization of single-photons.

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arXiv2014

Linear optical demonstration of quantum speed-up with a single qudit

Though quantum algorithm acts as an important role in quantum computation science, not only for providing a great vision for solving classically unsolvable problems, but also due to the fact that it gives a potential way of understanding quantum physics, the origin of the power of quantum algorithm is still an open question. Non-classical correlation is regarded as the most possible answer for the open question. However we experimentally realize a quantum speed-up algorithm on four-level system with linear optical elements and prove that even a single qudit is enough for designing an oracle-based algorithm which can solve a model problem twice faster than any classical algorithm. The algorithm can be generalized to higher dimensional qudits with the same two-to-one speed-up ratio.

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arXiv2014

Experimental realization of a generalized measuring device via a one-dimensional photonic quantum walk

We demonstrate an implementation of unambiguous state discrimination of two equally probable single-qubit states via a one-dimensional photonic quantum walk experimentally. Furthermore we experimentally realize a quantum walk algorithm for implementing a generalized measurement in terms of positive operator value measurement on a single qubit. The measurement of the single-photons' positions corresponds to a measurement of an element of the positive operator value measurement on the polarizations of the single-photons.

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arXiv2014

Realization of a quantum walk in phase space using resonator-assisted double quantum dots

We implement a quantum walk in phase space with a new mechanism based on the superconducting resonator-assisted double quantum dots. By analyzing the hybrid system, we obtain the necessary factors of realization of a quantum walk in phase space: the walker, coin, coin flipping and conditional phase shift. In order to implement the coin flipping operator, we add a driving field to the resonator. The interaction between the quantum dots and resonator field is used to implement conditional phase shift. Furthermore, we show with different driving fields the quantum walk in phase space exhibits a ballistic behavior over 25 steps and numerically analyze the factors which influence the spreading of the walker in phase space.

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arXiv2014

A one-dimensional quantum walk with multiple-rotation on the coin

We introduce and analyze a one-dimensional quantum walk with two time-independent rotations on the coin. We study the influence on the property of quantum walk due to the second rotation on the coin. Based on the asymptotic solution in the long time limit, a ballistic behaviour of this walk is observed. This quantum walk retains the quadratic growth of the variance if the combined operator of the coin rotations is unitary. That confirms no localization exhibits in this walk. This result can be extended to the walk with multiple time-independent rotations on the coin.

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arXiv2014

Perfect state transfer and efficient quantum routing: a discrete-time quantum walk approach

We show a perfect state transfer of an arbitrary unknown two-qubit state can be achieved via a discrete-time quantum walk with various settings of coin flippings, and extend this method to distribution of an arbitrary unknown multi-qubit entangled state between every pair of sites in the multi-dimensional network. Furthermore, we study the routing of quantum information on this network in a quantum walk architecture, which can be used as quantum information processors to communicate between separated qubits.

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arXiv2013

Observation of quasiperiodic dynamics in a one-dimensional quantum walk of single photons in space

We realize quasi-periodic dynamics of a quantum walker over 2.5 quasi-periods by realizing the walker as a single photon passing through a quantum-walk optical-interferometer network. We introduce fully controllable polarization-independent phase shifters in each optical path to realize arbitrary site-dependent phase shifts, and we employ large clear-aperture beam displacers, while maintaining high-visibility interference, to enable reaching 10 quantum-walk steps. By varying the half-wave-plate setting, we control the quantum-coin bias thereby observing a transition from quasi-periodic dynamics to ballistic diffusion.

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arXiv2013

Discrete time quantum walk with nitrogen-vacancy centers in diamond coupled to a superconducting flux qubit

We propose a quantum-electrodynamics scheme for implementing the discrete-time, coined quantum walk with the walker corresponding to the phase degree of freedom for a quasi-magnon field realized in an ensemble of nitrogen-vacancy centres in diamond. The coin is realized as a superconducting flux qubit. Our scheme improves on an existing proposal for implementing quantum walks in cavity quantum electrodynamics by removing the cumbersome requirement of varying drive-pulse durations according to mean quasiparticle number. Our improvement is relevant to all indirect-coin-flip cavity quantum-electrodynamics realizations of quantum walks. Our numerical analysis shows that this scheme can realize a discrete quantum walk under realistic conditions.

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arXiv2013

Non-Markovian Dynamics of Spin Squeezing

We evaluate the spin squeezing dynamics of N independent spin-1/2 particles with exchange symmetry. Each spin interacts with its own reservoir, and the reservoirs are independently and identical. The spin squeezing parameter is analytically calculated with different kinds of decoherence. The spin squeezing property vanishes with evolution time under the Markovian decoherence. Whereas coupled to the non-Markovian decoherence channels, the spin squeezing property collapses and revives with time. As spin squeezing can be regarded as a witness of multipartite entanglement, thus our scheme shows the collapse and revival of multipartite entanglement under non-Markovian decoherence.

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arXiv2013

Controlling and reversing the transition from classical diffusive to quantum ballistic transport in a quantum walk by driving the coin

We show that the standard quantum-walk quantum-to-classical transition, characterized by ballistic-to-diffusive spreading of the walker's position, can be controlled by externally modulating the coin state. We illustrate by showing an oscillation between classical diffusive and quantum ballistic spreading using numerical and asymptotically exact closed-form solutions, and we prove that the walker is in a controllable incoherent mixture of classical and quantum walks with a reversible quantum-to-classical transition.

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arXiv2012

Probing multipartite entanglement in a coupled Jaynes-Cummings system

We show how to probe multipartite entanglement in $N$ coupled Jaynes-Cummings cells where the degrees of freedom are the electronic energies of each of the $N$ atoms in separate single-mode cavities plus the $N$ single-mode fields themselves. Specifically we propose probing the combined system as though it is a dielectric medium. The spectral properties and transition rates directly reveal multipartite entanglement signatures. It is found that the Hilbert space of the $N$ cell system can be confined to the totally symmetric subspace of two states only that are maximally-entangled W states with 2N degrees of freedom.

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arXiv2012

Non-Markovian Decoherent Quantum Walks

Quantum walk acts obviously different from its classical counterpart, but decoherence will lessen and close the gap between them. To understand this process, it is necessary to investigate the evolution of quantum walk under different situation of decoherence. In this article, we study a non-Markovian decoherent quantum walk on a line. In the short time regime, the behavior of the walk deviates from both idea quantum walks and classical random walks. The position variance as a measure of quantum walk starts oscillating from the first several steps and tends to be linear on time and showing a diffusive spread in the long time limit, which is caused by the non-Markovian dephasing affecting on quantum correlations between quantum walker and his coin. We also study both quantum discord and measurement-induced disturbance as measures of quantum correlations and observe that both of them oscillate in the short time regime and tend to be zero in the long time limit. Therefore quantum walk with non-Markovian decoherence tends to diffusive spreading behavior in the long time limit, while in the short time regime it oscillates between a ballistic and diffusive spreading behavior, and the quantum correlation collapses and revivals due to the memory effect.

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arXiv2012

Spin Squeezing Property of Weighted Graph States

We study the spin squeezing property of weighted graph states, which can be used to improve the sensitivity in interferometry. Decoherence reduces the spin squeezing property but the result remains superior over other reference schemes with GHZ-type maximally entangled states and product states. We study the time evolution of spin squeezing of weighted graph states coupled to different decoherence channels. Based on the analysis, the spin squeezing of the weighted graph states is robust in the presence of decoherence and the decoherence limit in the improvement of the interferometric sensitivity is still achievable.

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arXiv2012

Implementation of multi-walker quantum walks with cavity grid

We show how multi-walker quantum walks can be implemented in a quantum quincunx created via cavity quantum electrodynamics. The implementation of a quantum walk with a multi-walker opens up the interesting possibility to introduce entanglement and more advanced walks. With different coin tosses and initial states the multi-walker quantum walk shows different probability distributions which deviate strongly from the classical random walks with quadratic enhanced spreadings and localization effects. By introducing decoherence, the transition from quantum walks to the classical versions is observed. We introduce the average fidelity decay as a signature to investigate the decoherence-induced irreversibility of quantum walks.

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arXiv2012

Two coupled Jaynes-Cummings cells

We develop a theoretical framework to evaluate the energy spectrum, stationary states, and dielectric susceptibility of two Jaynes-Cummings systems coupled together by the overlap of their respective longitudinal field modes, and we solve and characterize the combined system for the case that the two atoms and two cavities share a single quantum of energy.

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arXiv2012

Two quantum walkers sharing coins

We consider two independent quantum walks on separate lines augmented by partial or full swapping of coins after each step. For classical random walks, swapping or not swapping coins makes little difference to the random walk characteristics, but we show that quantum walks with partial swapping of coins have complicated yet elegant inter-walker correlations. Specifically we study the joint position distribution of the reduced two-walker state after tracing out the coins and analyze total, classical and quantum correlations in terms of the mutual information, the quantum mutual information, and the measurement-induced disturbance. Our analysis shows intriguing quantum features without classical analogues.

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arXiv2011

Compact source of narrow-band counterpropagating polarization-entangled photon pairs using a single dual-periodically poled crystal

We propose a scheme for the generation of counterpropagating polarization-entangled photon pairs from a dual-periodically poled crystal. Compared with the usual forward-wave type source, this source, in the backward-wave way, has a much narrower bandwidth. With a 2-cm-long bulk crystal, the bandwidths of the example sources are estimated to be 3.6 GHz, and the spectral brightnesses are more than 100 pairs/(s GHz mW). Two concurrent quasi-phase-matched spontaneous parametric down-conversion processes in a single crystal enable our source to be compact and stable. This scheme does not rely on any state projection and applies to both degenerate and non-degenerate cases, facilitating applications of the entangled photons.

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arXiv2011

Dangling-bond charge qubit on a silicon surface

Two closely spaced dangling bonds positioned on a silicon surface and sharing an excess electron are revealed to be a strong candidate for a charge qubit. Based on our study of the coherent dynamics of this qubit, its extremely high tunneling rate ~ 10^14 1/s greatly exceeds the expected decoherence rates for a silicon-based system, thereby overcoming a critical obstacle of charge qubit quantum computing. We investigate possible configurations of dangling bond qubits for quantum computing devices. A first-order analysis of coherent dynamics of dangling bonds shows promise in this respect.

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