20 research outputs found
Catalysis in Action via Elementary Thermal Operations
We investigate catalysis in the framework of elementary thermal operations,
making use of its unique advantages to illuminate catalytic dynamics. As
groundwork, we establish new technical tools that improve the computability of
state transition rules for elementary thermal operations, in particular,
providing a full characterization of state transitions for a qutrit system.
Using these tools in conjunction with numerical methods, we find that by
adopting even just a qubit catalyst, one can significantly enlarge the set of
state transitions for a qutrit system, largely closing the gap of reachable
states between elementary thermal operations and generic thermal operations. In
addition, we decompose catalytic transitions into time-resolved evolution, from
which the nonequilibrium free energy exchanges are tracked. Our results
document the existence of simple and practicable catalytic advantage in
thermodynamics, and demonstrate a way to analyse the mechanism of catalytic
processes.Comment: 15+19 pages; 9 figures; comments are welcome
Catalysis always degrades external quantum correlations
Catalysts used in quantum resource theories need not be in isolation and
therefore are possibly correlated with external systems, which the agent does
not have access to. Do such correlations help or hinder catalysis, and does the
classicality or quantumness of such correlations matter? To answer this
question, we first focus on the existence of a non-invasively measurable
observable that yields the same outcomes for repeated measurements, since this
signifies macro-realism, a key property distinguishing classical systems from
quantum systems. We show that a system quantumly correlated with an external
system so that the joint state is necessarily perturbed by any repeatable
quantum measurement, also has the same property against general quantum
channels. Our full characterization of such systems called totally quantum
systems, solves the open problem of characterizing tomographically sensitive
systems raised in [Lie and Jeong, Phys. Rev. Lett. 130, 020802 (2023)]. An
immediate consequence is that a totally quantum system cannot catalyze any
quantum process, even when a measure of correlation with its environment is
arbitrarily low. It generalizes to a stronger result, that the mutual
information of totally quantum systems cannot be used as a catalyst either.
These results culminate in the conclusion that, out of the correlations that a
generic quantum catalyst has with its environment, only classical correlations
allow for catalysis, and therefore using a correlated catalyst is equivalent to
using an ensemble of uncorrelated catalysts.Comment: 5+7 pages, 1 figure, Comments are welcom
Uniqueness of quantum state over time function
A fundamental asymmetry exists within the conventional framework of quantum
theory between space and time, in terms of representing causal relations via
quantum channels and acausal relations via multipartite quantum states. Such a
distinction does not exist in classical probability theory. In effort to
introduce this symmetry to quantum theory, a new framework has recently been
proposed, such that dynamical description of a quantum system can be
encapsulated by a static quantum state over time. In particular, Fullwood and
Parzygnat recently proposed the state over time function based on the Jordan
product as a promising candidate for such a quantum state over time function,
by showing that it satisfies all the axioms required in the no-go result by
Horsman et al. However, it was unclear if the axioms induce a unique state over
time function. In this work, we demonstrate that the previously proposed axioms
cannot yield a unique state over time function. In response, we therefore
propose an alternative set of axioms that is operationally motivated, and
better suited to describe quantum states over any spacetime regions beyond two
points. By doing so, we establish the Fullwood-Parzygnat state over time
function as the essentially unique function satisfying all these operational
axioms.Comment: 5+4 pages, comments welcom
Variance of Relative Surprisal as Single-Shot Quantifier
The variance of (relative) surprisal, also known as varentropy, so far mostly plays a role in information theory as quantifying the leading-order corrections to asymptotic independent and identically distributed (IID) limits. Here, we comprehensively study the use of it to derive single-shot results in (quantum) information theory. We show that it gives genuine sufficient and necessary conditions for approximate state transitions between pairs of quantum states in the single-shot setting, without the need for further optimization. We also clarify its relation to smoothed min and max entropies, and construct a monotone for resource theories using only the standard (relative) entropy and variance of (relative) surprisal. This immediately gives rise to enhanced lower bounds for entropy production in random processes. We establish certain properties of the variance of relative surprisal, which will be useful for further investigations, such as uniform continuity and upper bounds on the violation of subadditivity. Motivated by our results, we further derive a simple and physically appealing axiomatic single-shot characterization of (relative) entropy, which we believe to be of independent interest. We illustrate our results with several applications, ranging from interconvertibility of ergodic states, over Landauer erasure to a bound on the necessary dimension of the catalyst for catalytic state transitions and Boltzmann’s H theorem
Catalysis in Quantum Information Theory
Catalysts open up new reaction pathways which can speed up chemical reactions
while not consuming the catalyst. A similar phenomenon has been discovered in
quantum information science, where physical transformations become possible by
utilizing a (quantum) degree of freedom that remains unchanged throughout the
process. In this review, we present a comprehensive overview of the concept of
catalysis in quantum information science and discuss its applications in
various physical contexts.Comment: Review paper; Comments and suggestions welcome
Quantum Dynamic Programming
We introduce a quantum extension of dynamic programming, a fundamental
computational method for efficiently solving recursive problems using memory.
Our innovation lies in showing how to coherently generate unitaries of
recursion steps using memorized intermediate quantum states. We find that
quantum dynamic programming yields an exponential reduction in circuit depth
for a large class of fixed-point quantum recursions, including a known
recursive variant of the Grover's search. Additionally, we apply quantum
dynamic programming to a recently proposed double-bracket quantum algorithm for
diagonalization to obtain a new protocol for obliviously preparing a quantum
state in its Schmidt basis, providing a potential pathway for revealing
entanglement structures of unknown quantum states.Comment: 6 + 23 pages, 1 figur
By-passing fluctuation theorems
Fluctuation theorems impose constraints on possible work extraction probabilities in thermodynamical processes. These constraints are stronger than the usual second law, which is concerned only with average values. Here, we show that such constraints, expressed in the form of the Jarzysnki equality, can be by-passed if one allows for the use of catalysts---additional degrees of freedom that may become correlated with the system from which work is extracted, but whose reduced state remains unchanged so that they can be re-used. This violation can be achieved both for small systems but also for macroscopic many-body systems, and leads to positive work extraction per particle with finite probability from macroscopic states in equilibrium. In addition to studying such violations for a single system, we also discuss the scenario in which many parties use the same catalyst to induce local transitions. We show that there exist catalytic processes that lead to highly correlated work distributions, expected to have implications for stochastic and quantum thermodynamics
The variance of relative surprisal as single-shot quantifier
The variance of (relative) surprisal (also known as varentropy) so far mostly
plays a role in information theory as quantifying the leading order corrections
to asymptotic i. i. d. limits. Here, we comprehensively study the use of it to
derive single-shot results in (quantum) information theory. We show that it
gives genuine sufficient and necessary conditions for approximate single-shot
state-transitions in generic resource theories without the need for further
optimization. We also clarify its relation to smoothed min- and max-entropies,
and construct a monotone for resource theories using only the standard
(relative) entropy and variance of (relative) surprisal. This immediately gives
rise to enhanced lower bounds for entropy production in random processes. We
establish certain properties of the variance of relative surprisal which will
be useful for further investigations, such as uniform continuity and upper
bounds on the violation of sub-additivity. Motivated by our results, we further
derive a simple and physically appealing axiomatic single-shot characterization
of (relative) entropy which we believe to be of independent interest. We
illustrate our results with several applications, ranging from
interconvertibility of ergodic states, over Landauer erasure to a bound on the
necessary dimension of the catalyst for catalytic state transitions and
Boltzmann's H-theorem.Comment: 12+17 page
Clinical Sequencing Exploratory Research Consortium: Accelerating Evidence-Based Practice of Genomic Medicine
Despite rapid technical progress and demonstrable effectiveness for some types of diagnosis and therapy, much remains to be learned about clinical genome and exome sequencing (CGES) and its role within the practice of medicine. The Clinical Sequencing Exploratory Research (CSER) consortium includes 18 extramural research projects, one National Human Genome Research Institute (NHGRI) intramural project, and a coordinating center funded by the NHGRI and National Cancer Institute. The consortium is exploring analytic and clinical validity and utility, as well as the ethical, legal, and social implications of sequencing via multidisciplinary approaches; it has thus far recruited 5,577 participants across a spectrum of symptomatic and healthy children and adults by utilizing both germline and cancer sequencing. The CSER consortium is analyzing data and creating publically available procedures and tools related to participant preferences and consent, variant classification, disclosure and management of primary and secondary findings, health outcomes, and integration with electronic health records. Future research directions will refine measures of clinical utility of CGES in both germline and somatic testing, evaluate the use of CGES for screening in healthy individuals, explore the penetrance of pathogenic variants through extensive phenotyping, reduce discordances in public databases of genes and variants, examine social and ethnic disparities in the provision of genomics services, explore regulatory issues, and estimate the value and downstream costs of sequencing. The CSER consortium has established a shared community of research sites by using diverse approaches to pursue the evidence-based development of best practices in genomic medicine