Quantum memories at finite temperature

Brown, Benjamin J.; Loss, Daniel; Pachos, Jiannis K.; Self, Chris N.; Wootton, James R.

doi:10.1103/revmodphys.88.045005

Cited by 199 publications

(242 citation statements)

References 247 publications

(516 reference statements)

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“…β → ∞), there is no energy in the environment nor in the initial state of the chain, so the system state is confined to the zero-energy sector, where no local interaction couplesm 1 andm 2 ; thus information survives indefinitely. This ideal regime is approached exponentially in 1/T , what is usually called an Arrhenius activation law [12]; however, we observe that the characteristic energy scale is different depending on whether one has full access to the system or is confined to the zero-modes. Once again, most of the information loss observed when acting on the edge modes only would actually be recoverable via a global operation, and only a tiny fraction is fatally lost to the environment.…”

Section: Environment At Finite Temperaturementioning

confidence: 70%

“…In order to present the demonstration, we shall introduce the adjoint (or Heisenberg-picture) reduced channel D * t : ifÂ andB are polynomials in the zero-modes, then (13) which implies the definition in Eq. (12).…”

Section: Dynamics Under Noise and Decoding Of Informationmentioning

confidence: 99%

“…The use of F opt as a figure of merit is an important difference between our discussion and previous work in which a specific physically-motivated class of recovery operations is considered (e.g. stabilizer codes, minimal weight perfect matching) [11,12]. The optimal recovery fidelity represents a general upper limit to the performance of any possible recovery protocol, including all schemes previously considered in the literature.…”

Section: B Recovery Fidelity and Average Paritymentioning

confidence: 99%

“…The situation is analogous to that discussed in Refs. [41,44] for the Kitaev chain and in several works for the toric code coupled to a thermal environment [11,12]. The term L 0 is given by processes that do not exchange energy between the system and the environment.…”

Section: A Definition Of the Master Equationmentioning

confidence: 99%

“…Notwithstanding the impressive progress in the experimental control of genuine quantum systems [1][2][3][4][5][6][7][8][9], the reliable storage of quantum information over long times remains a problem of exceptional difficulty [10][11][12]. Among the ideas which have been put forward to solve this issue, proposals based on systems featuring topological order are among the most intriguing [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

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Quantum memories with zero-energy Majorana modes and experimental constraints

et al. 2016

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In this work we address the problem of realizing a reliable quantum memory based on zeroenergy Majorana modes in the presence of experimental constraints on the operations aimed at recovering the information. In particular, we characterize the best recovery operation acting only on the zero-energy Majorana modes and the memory fidelity that can be therewith achieved. In order to understand the effect of such restriction, we discuss two examples of noise models acting on the topological system and compare the amount of information that can be recovered by accessing either the whole system, or the zero-modes only, with particular attention to the scaling with the size of the system and the energy gap. We explicitly discuss the case of a thermal bosonic environment inducing a parity-preserving Markovian dynamics in which the memory fidelity achievable via a read-out of the zero modes decays exponentially in time, independent from system size. We argue, however, that even in the presence of said experimental limitations, the Hamiltonian gap is still beneficial to the storage of information.

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Section: Environment At Finite Temperaturementioning

confidence: 70%

Section: Dynamics Under Noise and Decoding Of Informationmentioning

confidence: 99%

Section: B Recovery Fidelity and Average Paritymentioning

confidence: 99%

Section: A Definition Of the Master Equationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantum memories with zero-energy Majorana modes and experimental constraints

et al. 2016

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Distributed Encoding and Decoding of Quantum Information over Networks

Yamasaki

Murao

2018

Adv Quantum Tech

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Encoding and decoding quantum information in a multipartite quantum system are indispensable for quantum error correction and also play crucial roles in multiparty tasks in distributed quantum information processing such as quantum secret sharing. To quantitatively characterize nonlocal properties of multipartite quantum transformations for encoding and decoding, we analyze the entanglement costs of encoding and decoding quantum information in a multipartite quantum system distributed among spatially separated parties connected by a network. This analysis generalizes previous studies of entanglement costs for preparing bipartite and multipartite quantum states and implementing bipartite quantum transformations by entanglement‐assisted local operations and classical communication (LOCC). We identify conditions for the parties being able to encode or decode quantum information in the distributed quantum system deterministically and exactly, when inter‐party quantum communication is restricted to a tree‐topology network. In our analysis, we reduce the multiparty tasks of implementing the encoding and decoding to sequential applications of one‐shot zero‐error quantum state splitting and merging for two parties. While encoding and decoding are inverse tasks of each other, our results suggest that a quantitative difference in entanglement cost between encoding and decoding arises due to the difference between quantum state merging and splitting.

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Magnetic Properties of Self‐Assemble Naphthalene Diimide Radical Aggregates

He,

Zhao,

Yao

et al. 2024

Small

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The concept of creating room‐temperature ferromagnets from organic radicals proposed nearly sixty years ago, has recently experienced a resurgence due to advances in organic radical chemistry and materials. However, the lack of definitive design paradigms for achieving stable long‐range ferromagnetic coupling between organic radicals presents an uncertain future for this research. Here, an innovative strategy is presented to achieve room‐temperature ferromagnets by assembling π‐conjugated radicals into π‐π stacking aggregates. These aggregates, with ultra‐close π‐π distances and optimal π‐π overlap, provide a platform for strong ferromagnetic (FM) interaction. The planar aromatic naphthalene diimide (NDI) anion radicals form nanorod aggregates with a π‐π distance of just 3.26 Å, shorter than typical van der Waals distances. The suppressed electron paramagnetic resonance (EPR) signal and emergent near‐infrared (NIR) absorption of the aggregates confirm strong interactions between the radicals. Magnetic measurements of NDI anion radical aggregates demonstrate room‐temperature ferromagnetism with a saturated magnetization of 1.1 emu g−1, the highest among pure organic ferromagnets. Theoretical calculations reveal that π‐stacks of NDI anion radicals with specific interlayer translational slippage favor ferromagnetic coupling over antiferromagnetic coupling.

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Quantum memories at finite temperature

Cited by 199 publications

References 247 publications

Quantum memories with zero-energy Majorana modes and experimental constraints

Quantum memories with zero-energy Majorana modes and experimental constraints

Distributed Encoding and Decoding of Quantum Information over Networks

Magnetic Properties of Self‐Assemble Naphthalene Diimide Radical Aggregates

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