Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1708.00700 · Quantum Information and Computation

Super-activating quantum memory with entanglement

Ji Guan, Yuan Feng, Mingsheng Ying

Published Nov 1, 2018• 1 citation
arXivHTMLPDF

Abstract

Noiseless subsystems were proved to be an efficient and faithful approach to preserve fragile information against decoherence in quantum information processing and quantum computation. They were employed to design a general (hybrid) quantum memory cell model that can store both quantum and classical information. In this paper, we find an interesting new phenomenon that the purely classical memory cell can be super-activated to preserve quantum states, whereas the null memory cell can only be super-activated to encode classical information. Furthermore, necessary and sufficient conditions for this phenomenon are discovered so that the super-activation can be easily checked by examining certain eigenvalues of the quantum memory cell without computing the noiseless subsystems explicitly. In particular, it is found that entangled and separable stationary states are responsible for the super-activation of storing quantum and classical information, respectively.

DOI
10.26421/qic18.13-14-3

Related papers

Super-Activation of Zero-Error Capacity of Noisy Quantum Channels

Runyao Duan

We study various super-activation effects in the following zero-error communication scenario: One sender wants to send classical or quantum information through a noisy quantum channel to one receiver with zero probability of error. First we show that there are quantum channels of which a single use is not able to transmit classical information perfectly yet two uses can. This is achieved by employing entangled input states between different uses of the given channel and thus cannot happen for classical channels. Second we exhibit a class of quantum channel with vanishing zero-error classical capacity such that when a noiseless qubit channel or one ebit shared entanglement are available, it can be used to transmit $\log_2 d$ noiseless qubits, where 2d is the dimension of input state space. Third we further construct quantum channels with vanishing zero-error classical capacity when assisted with classical feedback can be used to transmit both classical and quantum information perfectly. These striking findings not only indicate both the zero-error quantum and classical capacities of quantum channels satisfy a strong super-additivity beyond any classical channels, but also highlight the activation power of auxiliary physical resources in zero-error communication.

arXiv:0906.2527•Jun 15, 2009•54 citations

Entanglement sudden death in a quantum memory

Yaakov S. Weinstein

I explore the entanglement dynamics of multiqubit systems suitable for use as quantum memories: decoherence free subspaces and noiseless subsystems. The aim of this exploration is to determine how a complete loss of entanglement affects the ability of these error-avoidance techniques to protect quantum information. I utilize negativity and concurrence as entanglement measures and find no correlation between complete system loss of entanglement and the fidelity of the stored quantum information. These results complement previous results in which quantum protocols not explicitly based on entanglement exhibit little correlation between entanglement sudden death and the accuracy of the given protocol.

arXiv:0904.0956•Physical Review A•Aug 6, 2009•9 citations

Scheme for reducing decoherence in quantum computer memory

Peter W. Shor

Recently, it was realized that use of the properties of quantum mechanics might speed up certain computations dramatically. Interest has since been growing in the area of quantum computation. One of the main difficulties of quantum computation is that decoherence destroys the information in a superposition of states contained in a quantum computer, thus making long computations impossible. It is shown how to reduce the effects of decoherence for information stored in quantum memory, assuming that the decoherence process acts independently on each of the bits stored in memory. This involves the use of a quantum analog of errorcorrecting codes.Received 17 May 1995DOI:https://doi.org/10.1103/PhysRevA.52.R2493©1995 American Physical Society

Physical Review A•Oct 1, 1995•4,475 citations

Entangled states of signal pulses in multimode quantum memory

K. S. Tikhonov, T. Yu. Golubeva, Yu. M. Golubev

The possibility of preserving an entangled state of two signal pulses during writing and retrieval processes in a multimode quantum memory is investigated. Two stationary laser sources of light squeezed in two orthogonal quadratures are used for generation of the entangled state. “Carved out” pulses of appropriate duration are mixed on a symmetric beamsplitter, which allows obtaining the desired entanglement. It is assumed that each of the obtained entangled pulses is stored in a separate memory cell and subsequently retrieved from it. The obtained analytical expressions for Duan entanglement criterion are analyzed numerically for the case of broadband memory. It is demonstrated that the entanglement of pulses can be effectively preserved not only in the case of symmetric geometry of the experiment, wherein both pulses are written in two identical independent memory cells, but also in the case of different memory cells and even when one of the cells is absent completely. An important distinguishing feature of the problem under consideration, compared to the single mode case where high memory efficiency ensures good preservation of quantum properties of light, is the possibility of obtaining good preservation of entanglement at low memory efficiency (under shortened readout times).

Optics and Spectroscopy•May 1, 2015•5 citations

Quantum Communication with Redundancy-free Error Correction

Sándor Imre

The limits of classical information theory are stretched at several points by the consideration of quantum mechanics. Entanglement in itself is a unique phenomenon, and its application has enabled solutions such as super-dense compression, teleportation or super-activation of quantum channels. Noisy classical channels can only be made error-free by adding redundancy, and even this can only be done for certain channels. However, in this article, we examine an equally unique possibility, namely, what properties can make the quantum channels error-free without adding redundancy just by using appropriate quantum transformations. We will show the quantum coding required for this and illustrate its efficiency through examples.

•Aug 12, 2025•0 citations

On the emergence of quantum memory in non-Markovian dynamics

Alexander Yosifov, Aditya Iyer, Vlatko Vedral +1 more

The emergence of memory is a hallmark feature of non-Markovian dynamics. However, the type of memory -- classical or quantum -- required to realize certain dynamics remains unknown. We study the quantum homogenizer as a minimal model of non-Markovian evolution and identify the physical conditions under which genuinely quantum memory becomes necessary. Using entanglement measures and relying only on the local dynamics as a witness, we prove both analytically and numerically the type of memory depends not merely on the dynamics itself, but also on the reservoir's initial entanglement structure, and in particular the propagation of non-classical correlations within it. For different bi- or multi-partite reservoir initializations, we establish a correspondence between interaction strength and entanglement generation. We provide physical criteria and an activation lower bound for the onset of quantum memory. The results may inform us how environmental correlations govern the transition from classical to quantum memory in open quantum systems.

arXiv:2507.21907•Jul 29, 2025•0 citations
Noiseless subsystems were proved to be an efficient and faithful approach to preserve fragile information against decoherence in quantum information processing and quantum computation. They were employed to design a general (hybrid) quantum memory cell model that can store both quantum and classical information. In this paper, we find an interesting new phenomenon that the purely classical memory cell can be super-activated to preserve quantum states, whereas the null memory cell can only be super-activated to encode classical information. Furthermore, necessary and sufficient conditions for this phenomenon are discovered so that the super-activation can be easily checked by examining certain eigenvalues of the quantum memory cell without computing the noiseless subsystems explicitly. In particular, it is found that entangled and separable stationary states are responsible for the super-activation of storing quantum and classical information, respectively.
We study various super-activation effects in the following zero-error communication scenario: One sender wants to send classical or quantum information through a noisy quantum channel to one receiver with zero probability of error. First we show that there are quantum channels of which a single use is not able to transmit classical information perfectly yet two uses can. This is achieved by employing entangled input states between different uses of the given channel and thus cannot happen for classical channels. Second we exhibit a class of quantum channel with vanishing zero-error classical capacity such that when a noiseless qubit channel or one ebit shared entanglement are available, it can be used to transmit log⁡2d\log_2 dlog2​d noiseless qubits, where 2d is the dimension of input state space. Third we further construct quantum channels with vanishing zero-error classical capacity when assisted with classical feedback can be used to transmit both classical and quantum information perfectly. These striking findings not only indicate both the zero-error quantum and classical capacities of quantum channels satisfy a strong super-additivity beyond any classical channels, but also highlight the activation power of auxiliary physical resources in zero-error communication.
I explore the entanglement dynamics of multiqubit systems suitable for use as quantum memories: decoherence free subspaces and noiseless subsystems. The aim of this exploration is to determine how a complete loss of entanglement affects the ability of these error-avoidance techniques to protect quantum information. I utilize negativity and concurrence as entanglement measures and find no correlation between complete system loss of entanglement and the fidelity of the stored quantum information. These results complement previous results in which quantum protocols not explicitly based on entanglement exhibit little correlation between entanglement sudden death and the accuracy of the given protocol.
Recently, it was realized that use of the properties of quantum mechanics might speed up certain computations dramatically. Interest has since been growing in the area of quantum computation. One of the main difficulties of quantum computation is that decoherence destroys the information in a superposition of states contained in a quantum computer, thus making long computations impossible. It is shown how to reduce the effects of decoherence for information stored in quantum memory, assuming that the decoherence process acts independently on each of the bits stored in memory. This involves the use of a quantum analog of errorcorrecting codes.Received 17 May 1995DOI:https://doi.org/10.1103/PhysRevA.52.R2493©1995 American Physical Society
The possibility of preserving an entangled state of two signal pulses during writing and retrieval processes in a multimode quantum memory is investigated. Two stationary laser sources of light squeezed in two orthogonal quadratures are used for generation of the entangled state. “Carved out” pulses of appropriate duration are mixed on a symmetric beamsplitter, which allows obtaining the desired entanglement. It is assumed that each of the obtained entangled pulses is stored in a separate memory cell and subsequently retrieved from it. The obtained analytical expressions for Duan entanglement criterion are analyzed numerically for the case of broadband memory. It is demonstrated that the entanglement of pulses can be effectively preserved not only in the case of symmetric geometry of the experiment, wherein both pulses are written in two identical independent memory cells, but also in the case of different memory cells and even when one of the cells is absent completely. An important distinguishing feature of the problem under consideration, compared to the single mode case where high memory efficiency ensures good preservation of quantum properties of light, is the possibility of obtaining good preservation of entanglement at low memory efficiency (under shortened readout times).
The limits of classical information theory are stretched at several points by the consideration of quantum mechanics. Entanglement in itself is a unique phenomenon, and its application has enabled solutions such as super-dense compression, teleportation or super-activation of quantum channels. Noisy classical channels can only be made error-free by adding redundancy, and even this can only be done for certain channels. However, in this article, we examine an equally unique possibility, namely, what properties can make the quantum channels error-free without adding redundancy just by using appropriate quantum transformations. We will show the quantum coding required for this and illustrate its efficiency through examples.
The emergence of memory is a hallmark feature of non-Markovian dynamics. However, the type of memory -- classical or quantum -- required to realize certain dynamics remains unknown. We study the quantum homogenizer as a minimal model of non-Markovian evolution and identify the physical conditions under which genuinely quantum memory becomes necessary. Using entanglement measures and relying only on the local dynamics as a witness, we prove both analytically and numerically the type of memory depends not merely on the dynamics itself, but also on the reservoir's initial entanglement structure, and in particular the propagation of non-classical correlations within it. For different bi- or multi-partite reservoir initializations, we establish a correspondence between interaction strength and entanglement generation. We provide physical criteria and an activation lower bound for the onset of quantum memory. The results may inform us how environmental correlations govern the transition from classical to quantum memory in open quantum systems.