Yuxiang Yang

Last Name

Yang

First Name

Yuxiang

ORCID

0000-0002-0531-8929

Show all metadata

Search Results

Publications 1 - 10 of 25

The energy requirement of quantum processors
Chiribella, Giulio; Yang, Yuxiang; Renner, Renato (2019)
arXiv
We establish a general bound on the amount of energy required to implement quantum circuits and prove its achievability within a constant factor. The energy requirement for quantum circuits is independent of their time complexity, indicating a promising route to the design of future energy-efficient quantum processors. The bound on the energy requirement follows from a general argument on the realization of unitary gates in quantum resource theories, stating that the approximation of a resource-generating gate within an error $\epsilon$ requires an initial resource growing as $1/\sqrt \epsilon$ times the amount of resource generated by the gate.
Quantum Compression of Tensor Network States
Bai, Ge; Yang, Yuxiang; Chiribella, Giulio (2019)
arXiv
We design quantum compression algorithms for parametric families of tensor network states. We first establish an upper bound on the amount of memory needed to store an arbitrary state from a given state family. The bound is determined by the minimum cut of a suitable flow network, and is related to the flow of information from the manifold of parameters that specify the states to the physical systems in which the states are embodied. For given network topology and given edge dimensions, our upper bound is tight when all edge dimensions are powers of the same integer. When this condition is not met, the bound is optimal up to a multiplicative factor smaller than 1.585. We then provide a compression algorithm for general state families, and show that the algorithm runs in polynomial time for matrix product states.
Ultimate limit on time signal generation
Yang, Yuxiang; Renner, Renato (2020)
arXiv
The generation of time signals is a fundamental task in science. Here we study the relation between the quality of a time signal and the physics of the system that generates it. According to quantum theory, any time signal can be decomposed into individual quanta that lead to single detection events. Our main result is a bound on how sharply peaked in time these events can be, which depends on the dimension of the signal generator. This result promises applications in various directions, including information theory, quantum clocks, and process simulation.
Quantum metrology with indefinite causal order
Zhao, Xiaobin; Yang, Yuxiang; Chiribella, Giulio (2019)
arXiv
We address the study of quantum metrology enhanced by indefinite causal order, demonstrating a quadratic advantage in the estimation of the product of two average displacements in a continuous variable system. We prove that no setup where the displacements are probed in a fixed order can have root-mean-square error vanishing faster than the Heisenberg limit 1/N, where N is the number of displacements contributing to the average. In stark contrast, we show that a setup that probes the displacements in a superposition of two alternative orders yields a root-mean-square error vanishing with super-Heisenberg scaling 1/N^2. This result opens up the study of new measurement setups where quantum processes are probed in an indefinite order, and suggests enhanced tests of the canonical commutation relations, with potential applications to quantum gravity.
Covariant Quantum Error Correcting Codes via Reference Frames
Yang, Yuxiang; Mo, Yin; Renes, Joseph M.; et al. (2020)
arXiv
Error correcting codes with a universal set of transversal gates are the desiderata of realising quantum computing. Such codes, however, are ruled out by the Eastin-Knill theorem. Moreover, it also rules out codes which are covariant with respect to the action of transversal unitary operations forming continuous symmetries. In this work, starting from an arbitrary code, we construct approximate codes which are covariant with respect to local SU(d) symmetries using quantum reference frames. We show that our codes are capable of efficiently correcting different types of erasure errors. When only a small fraction of the n qudits upon which the code is built are erased, our covariant code has an error that scales as 1/n2, which is reminiscent of the Heisenberg limit of quantum metrology. When every qudit has a chance of being erased, our covariant code has an error that scales as 1/n. We show that the error scaling is optimal in both cases. Our approach has implications for fault-tolerant quantum computing, reference frame error correction, and the AdS-CFT duality.
Communication Cost of Quantum Processes
Yang, Yuxiang; Chiribella, Giulio; Hayashi, Masahito (2020)
IEEE Journal on Selected Areas in Information Theory
A common scenario in distributed computing involves a client who asks a server to perform a computation on a remote computer. An important problem is to determine the minimum amount of communication needed to specify the desired computation. Here we extend this problem to the quantum domain, analyzing the total amount of (classical and quantum) communication needed by a server in order to accurately execute a quantum process chosen by a client from a parametric family of quantum processes. We derive a general lower bound on the communication cost, establishing a relation with the precision limits of quantum metrology: if a v -dimensional family of processes can be estimated with mean squared error n−β by using n parallel queries, then the communication cost for n parallel executions of a process in the family is at least (βv/2−ϵ)logn qubits at the leading order in n , for every ϵ>0 . For a class of quantum processes satisfying the standard quantum limit ( β=1 ), we show that the bound can be attained by transmitting an approximate classical description of the desired process. For quantum processes satisfying the Heisenberg limit ( β=2 ), our bound shows that the communication cost is at least twice as the cost of communicating standard quantum limited processes with the same number of parameters.
Quantum Uncertainty Principles for Measurements with Interventions
Xiao, Yunlong; Yang, Yuxiang; Wang, Ximing; et al. (2023)
Physical Review Letters
Heisenberg's uncertainty principle implies fundamental constraints on what properties of a quantum system we can simultaneously learn. However, it typically assumes that we probe these properties via measurements at a single point in time. In contrast, inferring causal dependencies in complex processes often requires interactive experimentation - multiple rounds of interventions where we adaptively probe the process with different inputs to observe how they affect outputs. Here, we demonstrate universal uncertainty principles for general interactive measurements involving arbitrary rounds of interventions. As a case study, we show that they imply an uncertainty trade-off between measurements compatible with different causal dependencies.
Entropic time-energy uncertainty relations: an algebraic approach
Bertoni, Christian; Yang, Yuxiang; Renes, Joseph M. (2020)
New Journal of Physics
We address entropic uncertainty relations between time and energy or, more precisely, between measurements of an observableGand the displacementrof theG-generated evolution e(-irG). We derive lower bounds on the entropic uncertainty in two frequently considered scenarios, which can be illustrated as two different guessing games in which the role of the guessers are fixed or not. In particular, our bound for the first game improves the previous result by Coleset al[Phys. Rev. Lett.122100401 (2019)]. To derive our bounds, we extend a recently proposed novel algebraic method by Gaoet al[arXiv:1710.10038 [quant-ph]] which was used to derive both strong subadditivity and entropic uncertainty relations for measurements.
Quantum Metrology for Non-Markovian Processes
Altherr, Anian; Yang, Yuxiang (2021)
Physical Review Letters
Quantum metrology is a rapidly developing branch of quantum technologies. While various theories have been established on quantum metrology for Markovian processes, i.e., quantum channel estimation, quantum metrology for non-Markovian processes is much less explored. In this Letter, we establish a general framework of non-Markovian quantum metrology. For any parametrized non-Markovian process on a finite-dimensional system, we derive a formula for the maximal amount of quantum Fisher information that can be extracted from it by an optimally controlled probe state. In addition, we design an algorithm that evaluates this quantum Fisher information via semidefinite programming. We apply our framework to noisy frequency estimation, where we find that the optimal performance of quantum metrology is better in the non-Markovian scenario than in the Markovian scenario and explore the possibility of efficient sensing via simple variational circuits.
Energy requirement for implementing unitary gates on energy-unbounded systems
Yang, Yuxiang; Renner, Renato; Chiribella, Giulio (2022)
Journal of Physics A: Mathematical and Theoretical
The processing of quantum information always has a cost in terms of physical resources such as energy or time. Determining the resource requirements is not only an indispensable step in the design of practical devices-the resources need to be actually provided-but may also yield fundamental constraints on the class of processes that are physically possible. Here we study how much energy is required to implement a desired unitary gate on a quantum system with a non-trivial energy spectrum. We derive a general lower bound on the energy requirement, extending the main result of Chiribella et al (2021 Phys. Rev. X 11 021014) from finite dimensional systems to systems with unbounded Hamiltonians. Such an extension has immediate applications in quantum information processing with optical systems, and allows us to provide bounds on the energy requirement of continuous variable quantum gates, such as displacement and squeezing gates.

Publications 1 - 10 of 25

Yuxiang Yang

Last Name

First Name

ORCID

Organisational unit

Filters

Search Results