scholarly journals Emergent classicality in general multipartite states and channels

Quantum ◽  
2021 ◽  
Vol 5 ◽  
pp. 555
Author(s):  
Xiao-Liang Qi ◽  
Daniel Ranard
Keyword(s):  
Optimization Procedure ◽  
Quantum Channels ◽  
Channel State ◽  
Markov Blanket ◽  
Classical Information ◽  
Accessible Information ◽  
Measured System ◽  
Multipartite States ◽  
Total Environment ◽  
Quantum Measurement Process

In a quantum measurement process, classical information about the measured system spreads throughout the environment. Meanwhile, quantum information about the system becomes inaccessible to local observers. Here we prove a result about quantum channels indicating that an aspect of this phenomenon is completely general. We show that for any evolution of the system and environment, for everywhere in the environment excluding an O(1)-sized region we call the "quantum Markov blanket," any locally accessible information about the system must be approximately classical, i.e. obtainable from some fixed measurement. The result strengthens the earlier result of Brandão et al. (Nat. comm. 6:7908) in which the excluded region was allowed to grow with total environment size. It may also be seen as a new consequence of the principles of no-cloning or monogamy of entanglement. Our proof offers a constructive optimization procedure for determining the "quantum Markov blanket" region, as well as the effective measurement induced by the evolution. Alternatively, under channel-state duality, our result characterizes the marginals of multipartite states.

LIMITATION ON THE ACCESSIBLE INFORMATION FOR QUANTUM CHANNELS WITH INEFFICIENT MEASUREMENTS

2005 ◽  
Vol 03 (supp01) ◽  
pp. 87-95
Author(s):  
KURT JACOBS
Keyword(s):  
Quantum System ◽  
Von Neumann Entropy ◽  
Quantum Channels ◽  
Initial State ◽  
Von Neumann ◽  
Classical Information ◽  
Quantum Operations ◽  
Amount Of Information ◽  
Accessible Information

To transmit classical information using a quantum system, the sender prepares the system in one of a set of possible states and sends it to the receiver. The receiver then makes a measurement on the system to obtain information about the senders choice of state. The amount of information which is accessible to the receiver depends upon the encoding and the measurement. Here we derive a bound on this information which generalizes the bound derived by Schumacher, Westmoreland and Wootters [Schumacher, Westmoreland and Wootters, Phys. Rev. Lett. 76, 3452 (1996)] to include inefficient measurements, and thus all quantum operations. This also allows us to obtain a generalization of a bound derived by Hall [Hall, Phys. Rev. A 55, 100 (1997)], and to show that the average reduction in the von Neumann entropy which accompanies a measurement is concave in the initial state, for all quantum operations.

Generalized three-party sharing of operations on remote single qutrit

2014 ◽  
Vol 12 (03) ◽  
pp. 1450011 ◽  
Author(s):  
Pengfei Xing ◽  
Yimin Liu ◽  
Chuanmei Xie ◽  
Xiansong Liu ◽  
Zhanjun Zhang
Keyword(s):  
Success Probability ◽  
Entangled States ◽  
Entangled State ◽  
Quantum Channels ◽  
Channel State ◽  
Classical Communication ◽  
Maximally Entangled State ◽  
Quantum Operations ◽  
Local Operation ◽  
Maximally Entangled States

Two three-party schemes are put forward for sharing quantum operations on a remote qutrit with local operation and classical communication as well as shared entanglements. The first scheme uses a two-qutrit and three-qutrit non-maximally entangled states as quantum channels, while the second replaces the three-qutrit non-maximally entangled state with a two-qutrit. Both schemes are treated and compared from the four aspects of quantum and classical resource consumption, necessary-operation complexity, success probability and efficiency. It is found that the latter is overall more optimal than the former as far as a restricted set of operations is concerned. In addition, comparisons of both schemes with other four relevant ones are also made to show their two features, including degree generalization and channel-state generalization. Furthermore, some concrete discussions on both schemes are made to expose their important features of security, symmetry and experimental feasibility. Particularly, it is revealed that the success probabilities and intrinsic efficiencies in both schemes are completely determined by the shared entanglement.

scholarly journals QUANTUM SECURE CONDITIONAL DIRECT COMMUNICATION VIA EPR PAIRS

2005 ◽  
Vol 16 (08) ◽  
pp. 1293-1301 ◽  
Author(s):  
TING GAO ◽  
FENGLI YAN ◽  
ZHIXI WANG
Keyword(s):  
Secure Communication ◽  
Secret Message ◽  
Quantum Channels ◽  
Classical Communication ◽  
Direct Communication ◽  
Classical Information ◽  
Epr Pairs ◽  
Unitary Transformations ◽  
Local Measurements ◽  
The Common

Two schemes for quantum secure conditional direct communication are proposed, where a set of EPR pairs of maximally entangled particles in Bell states, initially made by the supervisor Charlie, but shared by the sender Alice and the receiver Bob, functions as quantum information channels for faithful transmission. After insuring the security of the quantum channel and obtaining the permission of Charlie (i.e., Charlie is trustworthy and cooperative, which means the "conditional" in the two schemes), Alice and Bob begin their private communication under the control of Charlie. In the first scheme, Alice transmits secret message to Bob in a deterministic manner with the help of Charlie by means of Alice's local unitary transformations, both Alice and Bob's local measurements, and both of Alice and Charlie's public classical communication. In the second scheme, the secure communication between Alice and Bob can be achieved via public classical communication of Charlie and Alice, and the local measurements of both Alice and Bob. The common feature of these protocols is that the communications between two communication parties Alice and Bob depend on the agreement of the third side Charlie. Moreover, transmitting one bit secret message, the sender Alice only needs to apply a local operation on her one qubit and send one bit classical information. We also show that the two schemes are completely secure if quantum channels are perfect.

Classical information transfer over noisy quantum channels

2003 ◽  
Vol 51 (45) ◽  
pp. 414-420
Author(s):  
C. Macchiavello ◽  
G.M. Palma
Keyword(s):  
Information Transfer ◽  
Quantum Channels ◽  
Classical Information

SPATIAL BELL STATE MEASUREMENT OF TWO PARTICLES

2005 ◽  
Vol 03 (01) ◽  
pp. 87-92 ◽  
Author(s):  
O. AKHAVAN ◽  
A. T. REZAKHANI ◽  
M. GOLSHANI
Keyword(s):  
Hilbert Space ◽  
Information Gain ◽  
Bell State ◽  
Quantum Channels ◽  
Cnot Gate ◽  
Logarithmic Factor ◽  
Bell State Measurement ◽  
Classical Information ◽  
State Measurement ◽  
Basic Position

Using spatial entanglement of two particles the rate of classical information gain has been increased by a logarithmic factor depending on the dimension of Hilbert space. To study Bell state measurement (BSM) of the two particles, at first, we have defined corresponding Bell bases in a typically general form. Then, the basic position gates are theoretically designed by side quantum channels and the usual CNOT gate. All the processes required in the BSM can be established based upon the introduced local and conditional basic gates.

scholarly journals The locking-decoding frontier for generic dynamics

2013 ◽  
Vol 469 (2159) ◽  
pp. 20130289 ◽  
Author(s):  
Frédéric Dupuis ◽  
Jan Florjanczyk ◽  
Patrick Hayden ◽  
Debbie Leung
Keyword(s):  
Mutual Information ◽  
Quantum Key Distribution ◽  
Black Hole Physics ◽  
Quantum Systems ◽  
Classical Information ◽  
Accessible Information ◽  
Generic Dynamics ◽  
Quantum Mutual Information ◽  
Logarithmic Number ◽  
Quantum Key Distribution Protocol

It is known that the maximum classical mutual information, which can be achieved between measurements on pairs of quantum systems, can drastically underestimate the quantum mutual information between them. In this article, we quantify this distinction between classical and quantum information by demonstrating that after removing a logarithmic-sized quantum system from one half of a pair of perfectly correlated bitstrings, even the most sensitive pair of measurements might yield only outcomes essentially independent of each other. This effect is a form of information locking but the definition we use is strictly stronger than those used previously. Moreover, we find that this property is generic, in the sense that it occurs when removing a random subsystem. As such, the effect might be relevant to statistical mechanics or black hole physics. While previous works had always assumed a uniform message, we assume only a min-entropy bound and also explore the effect of entanglement. We find that classical information is strongly locked almost until it can be completely decoded. Finally, we exhibit a quantum key distribution protocol that is ‘secure’ in the sense of accessible information but in which leakage of even a logarithmic number of bits compromises the secrecy of all others.

Sending classical information via noisy quantum channels

1997 ◽  
Vol 56 (1) ◽  
pp. 131-138 ◽  
Author(s):  
Benjamin Schumacher ◽  
Michael D. Westmoreland
Keyword(s):  
Quantum Channels ◽  
Classical Information
Sign in / Sign up

Export Citation Format

Share Document