<i>Colloquium</i>: Quantum coherence as a resource

Streltsov, Alexander; Adesso, Gerardo; Plenio, Martin B.

doi:10.1103/revmodphys.89.041003

Cited by 1,649 publications

(1,742 citation statements)

References 286 publications

(623 reference statements)

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“…Nevertheless, until very recently, there still lacks a rigorous information-theoretic framework for characterizing coherence and a great deal of effort has been devoted to this significant and long-standing topic [6]. Exploiting the quantum resource theory [7,8], Baumgratz et al proposed a framework for quantifying coherence based on distance or pseudo-distance measures [9], by noting that a similar line of thought has been successfully applied in the theory of quantum entanglement [10,11].…”

Section: Introductionmentioning

confidence: 99%

Maximal coherence in a generic basis

Yao

Dong

et al. 2016

Phys. Rev. A

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Since quantum coherence is an undoubted characteristic trait of quantum physics, the quantification and application of quantum coherence has been one of the long-standing central topics in quantum information science. Within the framework of a resource theory of quantum coherence proposed recently, a fiducial basis should be pre-selected for characterizing the quantum coherence in specific circumstances, namely, the quantum coherence is a basis-dependent quantity. Therefore, a natural question is raised: what are the maximum and minimum coherences contained in a certain quantum state with respect to a generic basis? While the minimum case is trivial, it is not so intuitive to verify in which basis the quantum coherence is maximal. Based on the coherence measure of relative entropy, we indicate the particular basis in which the quantum coherence is maximal for a given state, where the Fourier matrix (or more generally, complex Hadamard matrices) plays a critical role in determining the basis. Intriguingly, though we can prove that the basis associated with the Fourier matrix is a stationary point for optimizing the l 1 norm of coherence, numerical simulation shows that it is not a global optimal choice.

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Section: Introductionmentioning

confidence: 99%

Maximal coherence in a generic basis

Yao

Dong

et al. 2016

Phys. Rev. A

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“…As an extreme case, consider any CPTP map T that is not incoherent, but is a so-called "maximally incoherent operation" (MIO, cf. [16]), meaning that T (ρ) ∈ ∆ for all ρ ∈ ∆. This class was considered in [9], and it makes coherence theory asymptotically reversible [17], all states ρ being equivalent to C r (ρ) maximally coherent qubit states.…”

Section: Discussionmentioning

confidence: 99%

“…The present paper is concerned with this resource theory of coherence, and here we briefly recall its fundamental definitions, as well as some important coherence measures; for a comprehensive review, see [16]. Let {|i : i = 0, .…”

Section: Introductionmentioning

confidence: 99%

Resource theory of coherence: Beyond states

et al. 2017

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We generalize the recently proposed resource theory of coherence (or superposition) [Baumgratz, Cramer & Plenio, Phys. Rev. Lett. 113:140401; Winter & Yang, Phys. Rev. Lett. 116:120404] to the setting where not only the free ("incoherent") resources, but also the objects manipulated, are quantum operations rather than states.In particular, we discuss an information theoretic notion of coherence capacity of a quantum channel, and prove a single-letter formula for it in the case of unitaries. Then we move to the coherence cost of simulating a channel, and prove achievability results for unitaries and general channels acting on a d-dimensional system; we show that a maximally coherent state of rank d is always sufficient as a resource if incoherent operations are allowed, and rank d 2 for "strictly incoherent" operations. We also show lower bounds on the simulation cost of channels that allow us to conclude that there exists bound coherence in operations, i.e. maps with non-zero cost of implementing them but zero coherence capacity; this is in contrast to states, which do not exhibit bound coherence.

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“…This has fueled an intense effort to controllably generate linear superpositions in diverse physical systems, protect them from the decoherence processes, and develop tools that allow a quantitative characterization of coherence. Such characterization has been provided within the so-called resource theories, where the coherence resource can be acquired at a certain cost and is consumed to perform tasks of interest by means of constrained (incoherent) operations [159]. In the following, we report a few coherence quantifiers that, besides having a clear physical meaning, can directly relate the degree of coherence of a given stateρ to its off-diagonal matrix elements, the coherences ρ ij .…”

Section: General Coherence Quantifiersmentioning

confidence: 99%

Quantum modeling of ultrafast photoinduced charge separation

Rozzi

Troiani

Tavernelli

2017

J. Phys.: Condens. Matter

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Phenomena involving electron transfer are ubiquitous in nature, photosynthesis and enzymes or protein activity being prominent examples. Their deep understanding thus represents a mandatory scientific goal. Moreover, controlling the separation of photogenerated charges is a crucial prerequisite in many applicative contexts, including quantum electronics, photo-electrochemical water splitting, photocatalytic dye degradation, and energy conversion. In particular, photoinduced charge separation is the pivotal step driving the storage of sun light into electrical or chemical energy. If properly mastered, these processes may also allow us to achieve a better command of information storage at the nanoscale, as required for the development of molecular electronics, optical switching, or quantum technologies, amongst others.In this Topical review we survey recent progress in the understanding of ultrafast charge separation from photoexcited states. We report the state-of-the-art of the observation and theoretical description of charge separation phenomena in the ultrafast regime mainly focusing on molecularand nano-sized solar energy conversion systems. In particular, we examine different proposed mechanisms driving ultrafast charge dynamics, with particular regard to the role of quantum coherence and electron-nuclear coupling, and link experimental observations to theoretical approaches based either on model Hamiltonians or on first principles simulations.

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Colloquium: Quantum coherence as a resource

Cited by 1,649 publications

References 286 publications

Maximal coherence in a generic basis

Maximal coherence in a generic basis

Resource theory of coherence: Beyond states

Quantum modeling of ultrafast photoinduced charge separation

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