We establish the Stinespring dilation theorem of the link product of quantum channels in two different ways,discuss the discrimination of quantum channels,and show that the distinguishability can be improved by self-l...We establish the Stinespring dilation theorem of the link product of quantum channels in two different ways,discuss the discrimination of quantum channels,and show that the distinguishability can be improved by self-linking each quantum channel n times as n grows.We also find that the maximum value of Uhlmann's theorem can be achieved for diagonal channels.展开更多
Based on the quantum technique of the weak measurement and quantum measurement reversal(WMR),we propose a scheme to protect entanglement for an entangled two-qubit pure state from four typical quantum noise channels w...Based on the quantum technique of the weak measurement and quantum measurement reversal(WMR),we propose a scheme to protect entanglement for an entangled two-qubit pure state from four typical quantum noise channels with memory,i.e.,the amplitude damping channel,the phase damping channel,the bit flip channel,and the depolarizing channel.For a given initial state |Ψ>=a |00>+d|11>,it is found that the WMR operation indeed helps to protect entanglement from the above four quantum channels with memory,and the protection effect of WMR scheme is better when the coefficient a is small.For the other initial state |φ>=b|01>+c|10>,the effect of the protection scheme is the same regardless of the coefficient b and the WMR operation can protect entanglement in the amplitude damping channel with memory.Moreover,the protection of entanglement in quantum noise channels without memory in contrast to the results of the channels with memory is more effective.For |Ψ> or |φ>,we also find that the memory parameters play a significant role in the suppression of entanglement sudden death and the initial entanglement can be drastically amplified.Another more important result is that the relationship between the concurrence,the memory parameter,the weak measurement strength,and quantum measurement reversal strength is found through calculation and discussion.It provides a strong basis for the system to maintain maximum entanglement in the nosie channel.展开更多
A protocol for quantum dialogue is proposed to exchange directly the communicator＇s secret messages by using a three-dimensional Bell state and a two-dimensional Bell state as quantum channel with quantum superdence ...A protocol for quantum dialogue is proposed to exchange directly the communicator＇s secret messages by using a three-dimensional Bell state and a two-dimensional Bell state as quantum channel with quantum superdence coding, local collective unitary operations, and entanglement swapping. In this protocol, during the process of trans- mission of particles, the transmitted particles do not carry any secret messages and are transmitted only one time. The protocol has higher source capacity than protocols using symmetric two-dimensional states. The security is ensured by the unitary operations randomly performed on all checking groups before the particle sequence is transmitted and the application of entanglement swapping.展开更多
The private quantum channel (PQC) maps any quantum state to the maximally mixed state for the discrete as well as the bosonic Gaussian quantum systems, and it has fundamental meaning on the quantum cryptographic tasks...The private quantum channel (PQC) maps any quantum state to the maximally mixed state for the discrete as well as the bosonic Gaussian quantum systems, and it has fundamental meaning on the quantum cryptographic tasks and the quantum channel capacity problems. In this paper, we primally introduce a notion of approximate private quantum channel (<em>ε</em>-PQC) on <em>fermionic</em> Gaussian systems (<em>i.e.</em>, <em>ε</em>-FPQC), and construct its explicit form of the fermionic (Gaussian) private quantum channel. First of all, we suggest a general structure for <em>ε</em>-FPQC on the fermionic Gaussian systems with respect to the Schatten <em>p</em>-norm class, and then we give an explicit proof of the statement in the trace norm case. In addition, we study that the cardinality of a set of fermionic unitary operators agrees on the <em>ε</em>-FPQC condition in the trace norm case. This result may give birth to intuition on the construction of emerging fermionic Gaussian quantum communication or computing systems.展开更多
A potential acceleration of a quantum open system is of fundamental interest in quantum computation, quantum communication, and quantum metrology. In this paper, we investigate the ＂quantum speed-up capacity＂ which ...A potential acceleration of a quantum open system is of fundamental interest in quantum computation, quantum communication, and quantum metrology. In this paper, we investigate the ＂quantum speed-up capacity＂ which reveals the potential ability of a quantum system to be accelerated. We explore the evolutions of the speed-up capacity in different quantum channels for two-qubit states. We find that although the dynamics of the capacity is varying in different kinds of channels, it is positive in most situations which are considered in the context except one case in the amplitude-damping channel. We give the reasons for the different features of the dynamics. Anyway, the speed-up capacity can be improved by the memory effect. We find two ways which may be used to control the capacity in an experiment： selecting an appropriate coefficient of an initial state or changing the memory degree of environments.展开更多
We investigate how the correlated actions of quantum channels affect the robustness of entangled states.We consider the Bell-like state and random two-qubit pure states in the correlated depolarizing,bit flip,bit-phas...We investigate how the correlated actions of quantum channels affect the robustness of entangled states.We consider the Bell-like state and random two-qubit pure states in the correlated depolarizing,bit flip,bit-phase flip,and phase flip channels.It is found that the robustness of two-qubit pure states can be noticeably enhanced due to the correlations between consecutive actions of these noisy channels,and the Bell-like state is always the most robust one.We also consider the robustness of three-qubit pure states in correlated noisy channels.For the correlated bit flip and phase flip channels,the result shows that although the most robust and most fragile states are locally unitary equivalent,they exhibit different robustness in different correlated channels,and the effect of channel correlations on them is also significantly different.However,for the correlated depolarizing and bit-phase flip channels,the robustness of two special three-qubit pure states is exactly the same.Moreover,compared with the random three-qubit pure states,they are neither the most robust states nor the most fragile states.展开更多
A novel vertical stack heterostructure CMOSFET is investigated, which is structured by strained SiGe/Si with a hole quantum well channel in the compressively strained Sil-xGex layer for p-MOSFET and an electron quantu...A novel vertical stack heterostructure CMOSFET is investigated, which is structured by strained SiGe/Si with a hole quantum well channel in the compressively strained Sil-xGex layer for p-MOSFET and an electron quantum well channel in the tensile strained Si layer for n-MOSFET. The device possesses several advantages including： 1） the integration of electron quantum well channel with hole quantum well channel into the same vertical layer structure; 2） the gate work function modifiability due to the introduction of poly-SiGe as a gate material; 3） better transistor matching; and 4） flexibility of layout design of CMOSFET by adopting exactly the same material lays for both n-channel and p-channel. The MEDICI simulation result shows that p-MOSFET and n-MOSFET have approximately the same matching threshold voltages. Nice performances are displayed in transfer characteristic, transconductance and cut-off frequency. In addition, its operation as an inverter confirms the CMOSFET structured device to be normal and effective in function.展开更多
We investigate a quantum communication protocol, of so-called approximate quantum state sharing (AQSS), that protocol is basically based on pair of private quantum channels. In this paper, we prove that the scheme is ...We investigate a quantum communication protocol, of so-called approximate quantum state sharing (AQSS), that protocol is basically based on pair of private quantum channels. In this paper, we prove that the scheme is secure against any external and internal attacks of wiretapping in principle. Although the protocol leaks small amount of information corresponding to a security parameter , the scheme still preserves its information-theoretic security.展开更多
This paper investigates the change of entanglement for transmitting an arbitrarily entangled two-qubit pure state via one of three typical kinds of noisy quantum channels： amplitude damping quantum channel, phase dam...This paper investigates the change of entanglement for transmitting an arbitrarily entangled two-qubit pure state via one of three typical kinds of noisy quantum channels： amplitude damping quantum channel, phase damping quantum channel and depolarizing quantum channel. It finds, in all these three cases, that the output distant entanglement （measured by concurrence） reduces proportionately with respect to its initial amount, and the decaying ratio is determined only by the noisy characteristics of quantum channels and independent of the form of initial input state.展开更多
We propose a method to estimate the average fidelity using the unitary 2t-design of a twirled noisy channel, which is suitable for large-scale quantum circuits. Compared with the unitary 2-design in randomized benchma...We propose a method to estimate the average fidelity using the unitary 2t-design of a twirled noisy channel, which is suitable for large-scale quantum circuits. Compared with the unitary 2-design in randomized benchmarking, the unitary2t-design for the twirling of noisy channels is more flexible in construction and can provide more information. In addition,we prove that the proposed method provides an efficient and reliable estimation of the average fidelity in benchmarking multistage quantum gates and estimating the weakly gate-and time-dependent noise. For time-dependent noise, we provide a scheme of moment superoperator to analyze the noise in different experiments. In particular, we give a lower bound on the average fidelity of a channel with imperfect implementation of benchmarking and state preparation and measurement errors(SPAM).展开更多
Entanglement-assisted quantum error correction codes(EAQECCs)play an important role in quantum communications with noise.Such a scheme can use arbitrary classical linear code to transmit qubits over noisy quantum chan...Entanglement-assisted quantum error correction codes(EAQECCs)play an important role in quantum communications with noise.Such a scheme can use arbitrary classical linear code to transmit qubits over noisy quantum channels by consuming some ebits between the sender(Alice)and the receiver(Bob).It is usually assumed that the preshared ebits of Bob are error free.However,noise on these ebits is unavoidable in many cases.In this work,we evaluate the performance of EAQECCs with noisy ebits over asymmetric quantum channels and quantum channels with memory by computing the exact entanglement fidelity of several EAQECCs.We consider asymmetric errors in both qubits and ebits and show that the performance of EAQECCs in entanglement fidelity gets improved for qubits and ebits over asymmetric channels.In quantum memory channels,we compute the entanglement fidelity of several EAQECCs over Markovian quantum memory channels and show that the performance of EAQECCs is lowered down by the channel memory.Furthermore,we show that the performance of EAQECCs is diverse when the error probabilities of qubits and ebits are different.In both asymmetric and memory quantum channels,we show that the performance of EAQECCs is improved largely when the error probability of ebits is reasonably smaller than that of qubits.展开更多
Operator-valued frames are natural generalization of frames that have been used in many applied areas such as quantum computing, packets encoding and sensor networks. We focus on developing the theory about operator-v...Operator-valued frames are natural generalization of frames that have been used in many applied areas such as quantum computing, packets encoding and sensor networks. We focus on developing the theory about operator-valued frame generators for projective unitary representations of finite or countable groups which can be viewed as the theory of quantum channels with group structures. We present new results for operator-valued frames concerning (general and structured) dilation property, orthogonal frames, frame representation and dual frames. Our results are complementary to some of the recent work of Kaftal, Larson and Zhang, and in some cases our treatment is more elementary and transparent.展开更多
Based on the resource theory for quantifying the coherence of quantum channels, we introduce a new coherence quantifier for quantum channels via maximum relative entropy. We prove that the maximum relative entropy for...Based on the resource theory for quantifying the coherence of quantum channels, we introduce a new coherence quantifier for quantum channels via maximum relative entropy. We prove that the maximum relative entropy for coherence of quantum channels is directly related to the maximally coherent channels under a particular class of superoperations, which results in an operational interpretation of the maximum relative entropy for coherence of quantum channels. We also introduce the conception of subsuperchannels and sub-superchannel discrimination. For any quantum channels, we show that the advantage of quantum channels in sub-superchannel discrimination can be exactly characterized by the maximum relative entropy of coherence for quantum channels. Similar to the maximum relative entropy of coherence for channels, the robustness of coherence for quantum channels has also been investigated. We show that the maximum relative entropy of coherence for channels provides new operational interpretations of robustness of coherence for quantum channels and illustrates the equivalence of the dephasing-covariant superchannels,incoherent superchannels, and strictly incoherent superchannels in these two operational tasks.展开更多
The study of quantum channels is an important field and promises a wide range of applications, because any physical process can be represented as a quantum channel that transforms an initial state into a final state. ...The study of quantum channels is an important field and promises a wide range of applications, because any physical process can be represented as a quantum channel that transforms an initial state into a final state. Inspired by the method of performing non-unitary operators by the linear combination of unitary operations, we proposed a quantum algorithm for the simulation of the universal single-qubit channel, described by a convex combination of ＂quasi-extreme＂ channels corresponding to four Kraus operators, and is scalable to arbitrary higher dimension. We demonstrated the whole algorithm experimentally using the universal IBM cloud-based quantum computer and studied the properties of different qubit quantum channels. We illustrated the quantum capacity of the general qubit quantum channels, which quantifies the amount of quantum information that can be protected. The behavior of quantum capacity in different channels revealed which types of noise processes can support information transmission, and which types are too destructive to protect information. There was a general agreement between the theoretical predictions and the experiments, which strongly supports our method. By realizing the arbitrary quhit channel, this work provides a universally- accepted way to explore various properties of quantum channels and novel prospect for quantum communication.展开更多
We investigate nonlocal advantage of quantum coherence(NAQC)in a correlated dephasing channel modeled by themultimode bosonic reservoir.We obtain analytically the dephasing and memory factors of this channel for the r...We investigate nonlocal advantage of quantum coherence(NAQC)in a correlated dephasing channel modeled by themultimode bosonic reservoir.We obtain analytically the dephasing and memory factors of this channel for the reservoirhaving a Lorentzian spectral density,and analyze how they affect the NAQC defined by the l1 norm and relative entropy.It is shown that the memory effects of this channel on NAQC are state-dependent,and they suppress noticeably the rapiddecay of NAQC for the family of input Bell-like states with one excitation.For the given transmission time of each qubit,we also obtain the regions of the dephasing and memory factors during which there is NAQC in the output states.展开更多
In this paper [Commun. Theor. Phys. 53(2010) 648], Zhan et al. proposed a quantum dialogue protocol by using non-symmetric quantum channel. We study the security of the protocol and find that it has the drawback of in...In this paper [Commun. Theor. Phys. 53(2010) 648], Zhan et al. proposed a quantum dialogue protocol by using non-symmetric quantum channel. We study the security of the protocol and find that it has the drawback of information leakage. That is, Zhan et al.'s protocol is proved to be insecure by us.展开更多
Entanglement is the crucial resource for different quantum information processing tasks.While conventional studies focus on the entanglement of bipartite or multipartite quantum states,recent works have extended the s...Entanglement is the crucial resource for different quantum information processing tasks.While conventional studies focus on the entanglement of bipartite or multipartite quantum states,recent works have extended the scenario to the entanglement of quantum channels,an operational quantification of the channel entanglement manipulation capability.Based on the recently proposed channel entanglement resource framework,here we study a further task of resource detection—witnessing entanglement of quantum channels.We first introduce the general framework and show how channel entanglement detection is related to the Choi state of the channel,enabling channel entanglement detection via conventional state entanglement detection methods.We also consider entanglement of multipartite quantum channels and use the stabilizer formalism to construct entanglement witnesses for circuits consisting of controlled-Z gates.We study the effectiveness of the proposed detection methods and compare their performance for several typical channels.Our work paves the way for systematic theoretical studies of channel entanglement and practical benchmarking of noisy intermediate scaled quantum devices.展开更多
It was demonstrated that the entanglement evolution of a specially designed quantum state in the bistochastic channel is asymmetric. In this work, we generalize the study of the quantum correlations, including entangl...It was demonstrated that the entanglement evolution of a specially designed quantum state in the bistochastic channel is asymmetric. In this work, we generalize the study of the quantum correlations, including entanglement and quantum discord, evolution asymmetry to various quantum channels. We found that the asymmetry of entanglement and quantum discord only occurs in some special quantum channels, and the behavior of the entanglement evolution may be quite different from the behavior of the quantum discord evolution. To quantum entanglement, in some channels it decreases monotonously with the increase of the quantum channel intensity. In some other channels, when we increase the intensity of the quantum channel, it decreases at first, then keeps zero for some time, and then rises up. To quantum discord, the evolution becomes more complex and you may find that it evolutes unsmoothly at some points. These results illustrate the strong dependence of the quantum correlations evolution on the property of the quantum channels.展开更多
We investigate the effect of decoherence from a spin environment on the quantum channel capacity.Our results imply that the time evolution of the quantum channel capacity depends on the number of freedom degrees of th...We investigate the effect of decoherence from a spin environment on the quantum channel capacity.Our results imply that the time evolution of the quantum channel capacity depends on the number of freedom degrees of the environment,the tunneling element,the initial state of the environment,and the system-environment coupling strength.From the analysis,we find that the strong tunneling elements and the weak coupling strength can enhance the quantum channel capacity while the environment with a large number of freedom degrees and the strong coupling strength will shrink it.展开更多
We define the resource non-increasing(RNI)framework to study the dynamical resource theory.With this definition,we propose several potential quantification candidates under various free operation sets.For explicit dem...We define the resource non-increasing(RNI)framework to study the dynamical resource theory.With this definition,we propose several potential quantification candidates under various free operation sets.For explicit demonstrations,we quantify the quantum dynamical coherence in the scenarios with and without post-selective measurements.Correspondingly,we show that the maximally incoherent operations(MIO)and the incoherent operations(IO)in the static coherence resource theory are free in the sense of dynamical coherence.We also provide operational meanings for the measures by the quantum discrimination tasks.Moreover,for the dynamical total coherence,we also present convenient measures and give the analytic calculation for the amplitude damping channel.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61877054,12031004,and 12271474).
文摘We establish the Stinespring dilation theorem of the link product of quantum channels in two different ways,discuss the discrimination of quantum channels,and show that the distinguishability can be improved by self-linking each quantum channel n times as n grows.We also find that the maximum value of Uhlmann's theorem can be achieved for diagonal channels.
基金Project supported by the Natural Science Foundation of Shandong Province,China(Grant No.ZR2017MF040).
文摘Based on the quantum technique of the weak measurement and quantum measurement reversal(WMR),we propose a scheme to protect entanglement for an entangled two-qubit pure state from four typical quantum noise channels with memory,i.e.,the amplitude damping channel,the phase damping channel,the bit flip channel,and the depolarizing channel.For a given initial state |Ψ>=a |00>+d|11>,it is found that the WMR operation indeed helps to protect entanglement from the above four quantum channels with memory,and the protection effect of WMR scheme is better when the coefficient a is small.For the other initial state |φ>=b|01>+c|10>,the effect of the protection scheme is the same regardless of the coefficient b and the WMR operation can protect entanglement in the amplitude damping channel with memory.Moreover,the protection of entanglement in quantum noise channels without memory in contrast to the results of the channels with memory is more effective.For |Ψ> or |φ>,we also find that the memory parameters play a significant role in the suppression of entanglement sudden death and the initial entanglement can be drastically amplified.Another more important result is that the relationship between the concurrence,the memory parameter,the weak measurement strength,and quantum measurement reversal strength is found through calculation and discussion.It provides a strong basis for the system to maintain maximum entanglement in the nosie channel.
文摘A protocol for quantum dialogue is proposed to exchange directly the communicator＇s secret messages by using a three-dimensional Bell state and a two-dimensional Bell state as quantum channel with quantum superdence coding, local collective unitary operations, and entanglement swapping. In this protocol, during the process of trans- mission of particles, the transmitted particles do not carry any secret messages and are transmitted only one time. The protocol has higher source capacity than protocols using symmetric two-dimensional states. The security is ensured by the unitary operations randomly performed on all checking groups before the particle sequence is transmitted and the application of entanglement swapping.
文摘The private quantum channel (PQC) maps any quantum state to the maximally mixed state for the discrete as well as the bosonic Gaussian quantum systems, and it has fundamental meaning on the quantum cryptographic tasks and the quantum channel capacity problems. In this paper, we primally introduce a notion of approximate private quantum channel (<em>ε</em>-PQC) on <em>fermionic</em> Gaussian systems (<em>i.e.</em>, <em>ε</em>-FPQC), and construct its explicit form of the fermionic (Gaussian) private quantum channel. First of all, we suggest a general structure for <em>ε</em>-FPQC on the fermionic Gaussian systems with respect to the Schatten <em>p</em>-norm class, and then we give an explicit proof of the statement in the trace norm case. In addition, we study that the cardinality of a set of fermionic unitary operators agrees on the <em>ε</em>-FPQC condition in the trace norm case. This result may give birth to intuition on the construction of emerging fermionic Gaussian quantum communication or computing systems.
基金supported by the EU FP7 Marie–Curie Career Integration Fund(Grant No.631883)the Royal Society Research Fund(Grant No.RG150036)the Fundamental Research Fund for the Central Universities,China(Grant No.2018IB010)
文摘A potential acceleration of a quantum open system is of fundamental interest in quantum computation, quantum communication, and quantum metrology. In this paper, we investigate the ＂quantum speed-up capacity＂ which reveals the potential ability of a quantum system to be accelerated. We explore the evolutions of the speed-up capacity in different quantum channels for two-qubit states. We find that although the dynamics of the capacity is varying in different kinds of channels, it is positive in most situations which are considered in the context except one case in the amplitude-damping channel. We give the reasons for the different features of the dynamics. Anyway, the speed-up capacity can be improved by the memory effect. We find two ways which may be used to control the capacity in an experiment： selecting an appropriate coefficient of an initial state or changing the memory degree of environments.
基金the National Natural Science Foundation of China(Grant Nos.11705146 and 12175179)the Natural Science Basic Research Program of Shaanxi Province,China(Grant No.2019JQ-863)the Open Project of Shaanxi Key Laboratory for Theoretical Physics Frontiers(Grant No.SXKLTPF-K20190606)。
文摘We investigate how the correlated actions of quantum channels affect the robustness of entangled states.We consider the Bell-like state and random two-qubit pure states in the correlated depolarizing,bit flip,bit-phase flip,and phase flip channels.It is found that the robustness of two-qubit pure states can be noticeably enhanced due to the correlations between consecutive actions of these noisy channels,and the Bell-like state is always the most robust one.We also consider the robustness of three-qubit pure states in correlated noisy channels.For the correlated bit flip and phase flip channels,the result shows that although the most robust and most fragile states are locally unitary equivalent,they exhibit different robustness in different correlated channels,and the effect of channel correlations on them is also significantly different.However,for the correlated depolarizing and bit-phase flip channels,the robustness of two special three-qubit pure states is exactly the same.Moreover,compared with the random three-qubit pure states,they are neither the most robust states nor the most fragile states.
文摘A novel vertical stack heterostructure CMOSFET is investigated, which is structured by strained SiGe/Si with a hole quantum well channel in the compressively strained Sil-xGex layer for p-MOSFET and an electron quantum well channel in the tensile strained Si layer for n-MOSFET. The device possesses several advantages including： 1） the integration of electron quantum well channel with hole quantum well channel into the same vertical layer structure; 2） the gate work function modifiability due to the introduction of poly-SiGe as a gate material; 3） better transistor matching; and 4） flexibility of layout design of CMOSFET by adopting exactly the same material lays for both n-channel and p-channel. The MEDICI simulation result shows that p-MOSFET and n-MOSFET have approximately the same matching threshold voltages. Nice performances are displayed in transfer characteristic, transconductance and cut-off frequency. In addition, its operation as an inverter confirms the CMOSFET structured device to be normal and effective in function.
文摘We investigate a quantum communication protocol, of so-called approximate quantum state sharing (AQSS), that protocol is basically based on pair of private quantum channels. In this paper, we prove that the scheme is secure against any external and internal attacks of wiretapping in principle. Although the protocol leaks small amount of information corresponding to a security parameter , the scheme still preserves its information-theoretic security.
基金Project supported by the National Natural Science Foundation of China (Grant No 10775048)the National Fundamental Research Program of China (Grant No 2007CB925204)+1 种基金the Key Project of Chinese Ministry of Education (Grant No 206103)the Education Department of Hunan Province
文摘This paper investigates the change of entanglement for transmitting an arbitrarily entangled two-qubit pure state via one of three typical kinds of noisy quantum channels： amplitude damping quantum channel, phase damping quantum channel and depolarizing quantum channel. It finds, in all these three cases, that the output distant entanglement （measured by concurrence） reduces proportionately with respect to its initial amount, and the decaying ratio is determined only by the noisy characteristics of quantum channels and independent of the form of initial input state.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61372076 and 61701375)the 111 Project,China(Grant No.B08038)+1 种基金the Key Research and Development Plan of Shannxi Province,China(Grant No.BBD24017290001)the Foundation of Science and Technology on Communication Networks Laboratory,China(Grant No.KX172600031)
文摘We propose a method to estimate the average fidelity using the unitary 2t-design of a twirled noisy channel, which is suitable for large-scale quantum circuits. Compared with the unitary 2-design in randomized benchmarking, the unitary2t-design for the twirling of noisy channels is more flexible in construction and can provide more information. In addition,we prove that the proposed method provides an efficient and reliable estimation of the average fidelity in benchmarking multistage quantum gates and estimating the weakly gate-and time-dependent noise. For time-dependent noise, we provide a scheme of moment superoperator to analyze the noise in different experiments. In particular, we give a lower bound on the average fidelity of a channel with imperfect implementation of benchmarking and state preparation and measurement errors(SPAM).
基金Project supported by the National Key R&D Program of China (Grant No.2022YFB3103802)the National Natural Science Foundation of China (Grant Nos.62371240 and 61802175)the Fundamental Research Funds for the Central Universities (Grant No.30923011014)。
文摘Entanglement-assisted quantum error correction codes(EAQECCs)play an important role in quantum communications with noise.Such a scheme can use arbitrary classical linear code to transmit qubits over noisy quantum channels by consuming some ebits between the sender(Alice)and the receiver(Bob).It is usually assumed that the preshared ebits of Bob are error free.However,noise on these ebits is unavoidable in many cases.In this work,we evaluate the performance of EAQECCs with noisy ebits over asymmetric quantum channels and quantum channels with memory by computing the exact entanglement fidelity of several EAQECCs.We consider asymmetric errors in both qubits and ebits and show that the performance of EAQECCs in entanglement fidelity gets improved for qubits and ebits over asymmetric channels.In quantum memory channels,we compute the entanglement fidelity of several EAQECCs over Markovian quantum memory channels and show that the performance of EAQECCs is lowered down by the channel memory.Furthermore,we show that the performance of EAQECCs is diverse when the error probabilities of qubits and ebits are different.In both asymmetric and memory quantum channels,we show that the performance of EAQECCs is improved largely when the error probability of ebits is reasonably smaller than that of qubits.
基金supported by Singapore Ministry of Education Academic Research Fund Tier 1 (Grant No. R-146-000-136-112)National Natural Science Foundation of China (Grant No. 10771101)US National Science Foundation (Grant No. DMS-1106934)
文摘Operator-valued frames are natural generalization of frames that have been used in many applied areas such as quantum computing, packets encoding and sensor networks. We focus on developing the theory about operator-valued frame generators for projective unitary representations of finite or countable groups which can be viewed as the theory of quantum channels with group structures. We present new results for operator-valued frames concerning (general and structured) dilation property, orthogonal frames, frame representation and dual frames. Our results are complementary to some of the recent work of Kaftal, Larson and Zhang, and in some cases our treatment is more elementary and transparent.
基金supported by the National Natural Science Foundation of China(Grant Nos.11847209,61727801,and 12075159)the China Postdoctoral Science Foundation(Grant No.2019M650811)+4 种基金the China Scholarship Council(Grant No.201904910005)Shenzhen Institute for Quantum Science and Engineering,Southern University of Science and Technology(Grant No.SIQSE202001)Beijing Natural Science Foundation(Grant No.Z190005)the Academician Innovation Platform of Hainan ProvinceAcademy for Multidisciplinary Studies,Capital Normal University。
文摘Based on the resource theory for quantifying the coherence of quantum channels, we introduce a new coherence quantifier for quantum channels via maximum relative entropy. We prove that the maximum relative entropy for coherence of quantum channels is directly related to the maximally coherent channels under a particular class of superoperations, which results in an operational interpretation of the maximum relative entropy for coherence of quantum channels. We also introduce the conception of subsuperchannels and sub-superchannel discrimination. For any quantum channels, we show that the advantage of quantum channels in sub-superchannel discrimination can be exactly characterized by the maximum relative entropy of coherence for quantum channels. Similar to the maximum relative entropy of coherence for channels, the robustness of coherence for quantum channels has also been investigated. We show that the maximum relative entropy of coherence for channels provides new operational interpretations of robustness of coherence for quantum channels and illustrates the equivalence of the dephasing-covariant superchannels,incoherent superchannels, and strictly incoherent superchannels in these two operational tasks.
基金supported by the National Basic Research Program of China (Grant No. 2015CB921002)the National Natural Science Foundation of China (Grant Nos. 11175094, and 91221205)the Fund of Key Laboratory (Grant No. 9140C75010215ZK65001)
文摘The study of quantum channels is an important field and promises a wide range of applications, because any physical process can be represented as a quantum channel that transforms an initial state into a final state. Inspired by the method of performing non-unitary operators by the linear combination of unitary operations, we proposed a quantum algorithm for the simulation of the universal single-qubit channel, described by a convex combination of ＂quasi-extreme＂ channels corresponding to four Kraus operators, and is scalable to arbitrary higher dimension. We demonstrated the whole algorithm experimentally using the universal IBM cloud-based quantum computer and studied the properties of different qubit quantum channels. We illustrated the quantum capacity of the general qubit quantum channels, which quantifies the amount of quantum information that can be protected. The behavior of quantum capacity in different channels revealed which types of noise processes can support information transmission, and which types are too destructive to protect information. There was a general agreement between the theoretical predictions and the experiments, which strongly supports our method. By realizing the arbitrary quhit channel, this work provides a universally- accepted way to explore various properties of quantum channels and novel prospect for quantum communication.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11675129,11774406,and 11934018)the National Key R&D Program of China(Grant Nos.2016YFA0302104 and 2016YFA0300600)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)the Research Program of Beijing Academy of Quantum Information Sciences(Grant No.Y18G07).
文摘We investigate nonlocal advantage of quantum coherence(NAQC)in a correlated dephasing channel modeled by themultimode bosonic reservoir.We obtain analytically the dephasing and memory factors of this channel for the reservoirhaving a Lorentzian spectral density,and analyze how they affect the NAQC defined by the l1 norm and relative entropy.It is shown that the memory effects of this channel on NAQC are state-dependent,and they suppress noticeably the rapiddecay of NAQC for the family of input Bell-like states with one excitation.For the given transmission time of each qubit,we also obtain the regions of the dephasing and memory factors during which there is NAQC in the output states.
基金Supported by the 2014-Year Program for Excellent Youth Talents in University of Anhui Provincethe Talent Scientific Research Fundation of Tongling University under Grant No.2015tlxyrc01the Program for Academic Leader Reserve Candidates in Tongling University under Grant No.2014tlxyxs30
文摘In this paper [Commun. Theor. Phys. 53(2010) 648], Zhan et al. proposed a quantum dialogue protocol by using non-symmetric quantum channel. We study the security of the protocol and find that it has the drawback of information leakage. That is, Zhan et al.'s protocol is proved to be insecure by us.
基金supported by the National Natural Science Foundation of China under Grant Nos.62072119 and 61672007Guangdong Basic and Applied Basic Research Foundation under Grant No.2020A1515011180。
文摘Entanglement is the crucial resource for different quantum information processing tasks.While conventional studies focus on the entanglement of bipartite or multipartite quantum states,recent works have extended the scenario to the entanglement of quantum channels,an operational quantification of the channel entanglement manipulation capability.Based on the recently proposed channel entanglement resource framework,here we study a further task of resource detection—witnessing entanglement of quantum channels.We first introduce the general framework and show how channel entanglement detection is related to the Choi state of the channel,enabling channel entanglement detection via conventional state entanglement detection methods.We also consider entanglement of multipartite quantum channels and use the stabilizer formalism to construct entanglement witnesses for circuits consisting of controlled-Z gates.We study the effectiveness of the proposed detection methods and compare their performance for several typical channels.Our work paves the way for systematic theoretical studies of channel entanglement and practical benchmarking of noisy intermediate scaled quantum devices.
基金Supported by the National Natural Science Foundation of China under Grant Nos.61327901,61490711,61225025,11474268the Fundamental Research Funds for the Central Universities under Grant No.WK2470000018
文摘It was demonstrated that the entanglement evolution of a specially designed quantum state in the bistochastic channel is asymmetric. In this work, we generalize the study of the quantum correlations, including entanglement and quantum discord, evolution asymmetry to various quantum channels. We found that the asymmetry of entanglement and quantum discord only occurs in some special quantum channels, and the behavior of the entanglement evolution may be quite different from the behavior of the quantum discord evolution. To quantum entanglement, in some channels it decreases monotonously with the increase of the quantum channel intensity. In some other channels, when we increase the intensity of the quantum channel, it decreases at first, then keeps zero for some time, and then rises up. To quantum discord, the evolution becomes more complex and you may find that it evolutes unsmoothly at some points. These results illustrate the strong dependence of the quantum correlations evolution on the property of the quantum channels.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 11105001,11004001,and 10975125
文摘We investigate the effect of decoherence from a spin environment on the quantum channel capacity.Our results imply that the time evolution of the quantum channel capacity depends on the number of freedom degrees of the environment,the tunneling element,the initial state of the environment,and the system-environment coupling strength.From the analysis,we find that the strong tunneling elements and the weak coupling strength can enhance the quantum channel capacity while the environment with a large number of freedom degrees and the strong coupling strength will shrink it.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12175029,11775040,and12011530014)。
文摘We define the resource non-increasing(RNI)framework to study the dynamical resource theory.With this definition,we propose several potential quantification candidates under various free operation sets.For explicit demonstrations,we quantify the quantum dynamical coherence in the scenarios with and without post-selective measurements.Correspondingly,we show that the maximally incoherent operations(MIO)and the incoherent operations(IO)in the static coherence resource theory are free in the sense of dynamical coherence.We also provide operational meanings for the measures by the quantum discrimination tasks.Moreover,for the dynamical total coherence,we also present convenient measures and give the analytic calculation for the amplitude damping channel.
