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Xiang-Bin Wang

Publications and source records attributed to Xiang-Bin Wang.

At least 91 records · Page 5Linked to original sources
arXiv2013

General model for simulation of the measurement-device independent quantum key distribution

We present a general model on the simulation of the measurement-device independent quantum key distribution (MDI-QKD). It can be used to predict experimental observations of a MDI-QKD with linear channel loss, simulating corresponding values for the gains, the error rates in different basis, and also the final key rates. Our model can be applicable to the MDI-QKDs with whatever convex source states or using whatever coding schemes. Therefore, it is useful in characterizing and evaluating the performance of any MDI-QKD protocols, making it a valuable tool in studying the quantum key distributions.

quant-ph↗
arXiv2013

An efficient implementation of the decoy-state measurement-device-independent quantum key distribution with heralded single-photon sources

We study the decoy-state measurement-device-independent quantum key distribution using heralded single-photon sources. This has the advantage that the observed error rate in X basis is in higher order and not so large. We calculate the key rate and transmission distance for two cases: one using only triggered events, and the other using both triggered and non-triggered events. We compare the key rates of various protocols and find that our new scheme using triggered and non-triggered events can give higher key rate and longer secure distance. Moreover, we also show the different behavior of our scheme when using different heralded single-photon sources, i.e., in poisson or thermal distribution. We demonstrate that the former can generate a relatively higher secure key rate than the latter, and can thus work more efficiently in practical quantum key distributions.

quant-ph↗
arXiv2013

Fast creation of conditional quantum gate and entanglement using a common bath only

We propose a scheme to for fast conditional phase shift and creation entanglement of two qubits that interact with a common heat bath. Dynamical decoupling is applied in the scheme so that it works even in the regime of strong interaction between qubits and environment. Our scheme does not request any direct interaction between the two qubits.

quant-ph↗
arXiv2013

Quantum internet using code division multiple access

A crucial open problem in large-scale quantum networks is how to efficiently transmit quantum data among many pairs of users via a common data-transmission medium. We propose a solution by developing a quantum code division multiple access (q-CDMA) approach in which quantum information is chaotically encoded to spread its spectral content, and then decoded via chaos synchronization to separate different sender-receiver pairs. In comparison to other existing approaches, such as frequency division multiple access (FDMA), the proposed q-CDMA can greatly increase the information rates per channel used, especially for very noisy quantum channels.

quant-ph↗
arXiv2013

Three-intensity decoy state method for device independent quantum key distribution

We study the measurement device independent quantum key distribution (MDI-QKD) in practice with limited resource, when there are only 3 different states in implementing the decoy-state method. We present a more tightened explicit formula to estimate the lower bound of the yield of two-single-photon pulses. Moreover, we show that the bounding of this yield and phase flip error of single photon pulse pairs can be further improved by using other constraints which can be solved by a simple and explicit program. Results of numerical simulation for key rates with both the improved explicit formula and the program are presented. It shows that the results obtained with our methods here can significantly improve the key rate and secure distance of MDI QKD with only three intensities.

quant-ph↗
arXiv2013

Lossy Quantum Optical Metrology with Squeezed States

We study the precise phase estimation using squeezed states with photon losses present. Our exact quantum Fisher information calculation shows significant quantum enhancement and thus reveals the benchmark for practical quantum metrology in this noisy scenario. However, we find that the existing parity measurement scheme [P.M. Anisimov et al, Phys. Rev. Lett. 104, 103602 (2010)] behaves worse than even classical cases given very small losses, unless we take an appropriate loss dependent phase shift. Using our formulae, the two optimized aspects including the pre-detection phase shift and the consequent light intensity of a tradeoff strategy for photon resource arrangement can be both calculated. Therefore our result makes it possible to experimentally realize quantum metrology of phase estimation with squeezed states.

quant-ph↗
arXiv2013

Efficient tomography of quantum-optical Gaussian processes probed with a few coherent states

An arbitrary quantum-optical process (channel) can be completely characterized by probing it with coherent states using the recently developed coherent-state quantum process tomography (QPT) [Lobino et al., Science 322, 563 (2008)]. In general, precise QPT is possible if an infinite set of probes is available. Thus, realistic QPT of infinite-dimensional systems is approximate due to a finite experimentally-feasible set of coherent states and its related energy-cut-off approximation. We show with explicit formulas that one can completely identify a quantum-optical Gaussian process just with a few different coherent states without approximations like the energy cut-off. For tomography of multimode processes, our method exponentially reduces the number of different test states, compared with existing methods.

quant-ph↗
arXiv2013

Three-intensity decoy state method for device independent quantum key distribution with basis dependent errors

We study the measurement device independent quantum key distribution (MDIQKD) in practice with limited resource, when there are only 3 different states in implementing the decoy-state method and when there are basis dependent coding errors. We present general formulas for the decoy-state method for two-pulse sources with 3 different states, which can be applied to the recently proposed MDIQKD with imperfect single-photon source such as the coherent states or the heralded states from the parametric down conversion. We point out that the existing result for secure QKD with source coding errors does not always hold. We find that very accurate source coding is not necessary. In particular, we loosen the precision of existing result by several magnitude orders for secure QKD.

quant-ph↗
arXiv2013

Dynamic control of quantum geometric heat flux in a nonequilibrium spin-boson model

We study the quantum geometric heat flux in the nonequilibrium spin-boson model. By adopting the noninteracting-blip approximation that is able to accommodate the strong system-bath coupling, we show that there exists a nonzero geometric heat flux only when the two-level system is nondegenerate. Moreover, the pumping, no pumping, and dynamic control of geometric heat flux are discussed in detail, compared to the results with Redfield weak-coupling approximation. In particular, the geometric energy transfer induced by modulation of two system-bath couplings is identified, which is exclusive to quantum transport in the strong system-bath coupling regime.

cond-mat.mes-hall↗
arXiv2013

Operator Quantum Zeno Effect: Protecting Quantum Information with Noisy Two-Qubit Interactions

The time evolution of some quantum states can be slowed down or even stopped under frequent measurements. This is the usual quantum Zeno effect. Here, we report an operator quantum Zeno effect, in which the evolution of some physical observables is slowed down through measurements even though the quantum state changes randomly with time. Based on the operator quantum Zeno effect, we show how we can protect quantum information from decoherence with two-qubit measurements, realizable with noisy two-qubit interactions.

quant-ph↗
arXiv2011

Photon Induced Entanglement in Atom-Cavity Systems

We study the evolution of quantum entanglement in double cavity systems. The entanglement of cavity atoms induced by entangled pair of photons is investigated. Both entanglement sudden death and entanglement sudden birth phenomena are shown to be existed and analyzed in detail. We also propose a strategy to enhance the entanglement between the atom in one cavity and the photon in another cavity by using quantum Zeno effect.

quant-ph↗
arXiv2010

Optimal Quantum State Estimation with Use of the No-Signaling Principle

A simple derivation of the optimal state estimation of a quantum bit was obtained by using the no-signaling principle. In particular, the no-signaling principle determines a unique form of the guessing probability independently of figures of merit, such as the fidelity or information gain. This proves that the optimal estimation for a quantum bit can be achieved by the same measurement for almost all figures of merit.

quant-ph↗
arXiv2010

Protecting Two-Qubit Quantum States by $π$-Phase Pulses

We study the state decay of two qubits interacted with a common harmonic oscillator reservoir. There are both decoherence error and the error caused by the amplitude change of the superradiant state. We show that frequent $π$-phase pulses can eliminate both typpes of errors therefore protect a two-qubit odd-parity state more effectively than the frequent measurement method. This shows that the the methods using dynamical decoupling and the quantum Zeno effects actually can give rather {\em different} results when the operation frequency is finite.

quant-ph↗
arXiv2010

Efficient tomography of quantum processes

We show with explicit formulas that one can completely identify an unknown quantum process with only one weakly entangled state; and identify a quantum optical Gaussian process with either one two-mode squeezed state or a few different coherent states. In tomography of a multi-mode process, our method reduces the number of different test states exponentially compared with existing methods.

quant-ph↗
arXiv2010

Entanglement distribution maximization over one-side Gaussian noisy channel

The optimization of entanglement evolution for two-mode Gaussian pure states under one-side Gaussian map is studied. Even there isn't complete information about the one-side Gaussian noisy channel, one can still maximize the entanglement distribution by testing the channel with only two specific states.

quant-ph↗
arXiv2010

Secure quantum key distribution in an easy way

Secure quantum key distribution can be achieved with an imperfect single-photon source through implementing the decoy-state method. However, security of all those theoretical results of decoy-state method based on the original framework raised by Hwang needs monitoring the source state very carefully, because the elementary proposition that the counting rates of the same state from different sources are equal does not hold in general when the source is unstable. Source intensity monitoring greatly decreases the system efficiency. Here without using Hwang's proposition for stable source, we present a sufficient condition for a secure decoy-state protocol without monitoring the source intensity. The passive 2-intensity protocol proposed by Adachi, Yamamoto, Koashi, and Imoto(AYKI) (Phys. Rev. Lett. 99, 180503 (2007) satisfies the condition. Therefore, the protocol can always work securely without monitoring the source state or switching the source intensity. We also show that our result can greatly improve the key rate of the 3-intensity protocol with a fluctuating coherent-state source.

quant-ph↗
arXiv2009

On-demand Entanglement Source with Spatial Phase Modulation

The polarization entanglement photon pairs generated from the biexciton cascade decay in a single semiconductor quantum dot is corrupted by the position-dependent (time-dependent) phase difference of the two polarization mode due to the fine structure splitting. We show that, by taking voltage ramping to an electro-optic modulator, such phase-difference can be removed. In our first proposed set-up, two photons are sent to two separate Pockels cell under reverse voltage ramping, as a result, the position-dependent phase difference between the two polarization mode is removed in the outcome state. In our second proposed set-up, the polarization of the first photon is flipped and then both photons fly into the same Pokels cell. Since we only need to separate the two photons rather than separate the two polarization modes, our schemes are robust with respect to fluctuations of the optical paths.

quant-ph↗