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In this work, we show, for the well-studied problem of learning parity under noise, where a learner tries to learn $x=(x_1,\ldots,x_n) \in \{0,1\}^n$ from a stream of random linear equations over $\mathrm{F}_2$ that are correct with…

Machine Learning · Computer Science 2021-07-07 Sumegha Garg , Pravesh K. Kothari , Pengda Liu , Ran Raz

Stochastic processes underlie a vast range of natural and social phenomena. Some processes such as atomic decay feature intrinsic randomness, whereas other complex processes, e.g. traffic congestion, are effectively probabilistic because we…

Quantum neural networks (QNNs) have been a promising framework in pursuing near-term quantum advantage in various fields, where many applications can be viewed as learning a quantum state that encodes useful data. As a quantum analog of…

Quantum Physics · Physics 2023-09-27 Hao-kai Zhang , Chenghong Zhu , Mingrui Jing , Xin Wang

Cumulative memory -- the sum of space used per step over the duration of a computation -- is a fine-grained measure of time-space complexity that was introduced to analyze cryptographic applications like password hashing. It is a more…

Computational Complexity · Computer Science 2023-07-06 Paul Beame , Niels Kornerup

The query model offers a concrete setting where quantum algorithms are provably superior to randomized algorithms. Beautiful results by Bernstein-Vazirani, Simon, Aaronson, and others presented partial Boolean functions that can be computed…

Quantum Physics · Physics 2020-02-12 Avishay Tal

In order to evaluate, validate, and refine the design of new quantum algorithms or quantum computers, researchers and developers need methods to assess their correctness and fidelity. This requires the capabilities of quantum circuit…

Quantum Physics · Physics 2018-11-16 Xin-Chuan Wu , Sheng Di , Franck Cappello , Hal Finkel , Yuri Alexeev , Frederic T. Chong

Quantum data hiding stores classical information in bipartite quantum states that are, in principle, perfectly distinguishable, yet remain almost indistinguishable without access to a quantum communication channel. Here, we investigate…

Quantum Physics · Physics 2025-11-07 Aby Philip , Alexander Streltsov

We consider the problem of performing linear regression over a stream of $d$-dimensional examples, and show that any algorithm that uses a subquadratic amount of memory exhibits a slower rate of convergence than can be achieved without…

Machine Learning · Computer Science 2020-10-13 Vatsal Sharan , Aaron Sidford , Gregory Valiant

The energy cost of erasing quantum states depends on our knowledge of the states. We show that learning algorithms can acquire such knowledge to erase many copies of an unknown state at the optimal energy cost. This is proved by showing…

Quantum Physics · Physics 2025-12-30 Haimeng Zhao , Yuzhen Zhang , John Preskill

Simulating the stochastic evolution of real quantities on a digital computer requires a trade-off between the precision to which these quantities are approximated, and the memory required to store them. The statistical accuracy of the…

Quantum Physics · Physics 2017-10-16 Andrew J. P. Garner , Qing Liu , Jayne Thompson , Vlatko Vedral , Mile Gu

The problem of discriminating the state of a quantum system among a number of hypothetical states is usually addressed under the assumption that one has perfect knowledge of the possible states of the system. In this thesis, I analyze the…

Quantum Physics · Physics 2014-07-18 Gael Sentís

Quantum state tomography is the problem of estimating a given quantum state. Usually, it is required to run the quantum experiment - state preparation, state evolution, measurement - several times to be able to estimate the output quantum…

General Physics · Physics 2025-04-30 Shibdas Roy , Filippo Caruso , Srushti Patil , Anumita Mukhopadhyay

Large scale quantum information processing requires stable and long-lived quantum memories. Here, using atom-photon entanglement, we propose an experimentally feasible scheme to realize decoherence-free quantum memory with atomic ensembles,…

Quantum Physics · Physics 2008-11-05 Feng Mei , Ya-Fei Yu , Zhi-Ming Zhang

Interest in quantum machine learning is increasingly growing due to its potential to offer more efficient solutions for problems that are difficult to tackle with classical methods. In this context, the research work presented here focuses…

Quantum Physics · Physics 2025-04-11 A. De Lorenzis , M. P. Casado , M. P. Estarellas , N. Lo Gullo , T. Lux , F. Plastina , A. Riera , J. Settino

Recent years have seen significant activity on the problem of using data for the purpose of learning properties of quantum systems or of processing classical or quantum data via quantum computing. As in classical learning, quantum learning…

Quantum Physics · Physics 2024-04-17 Leonardo Banchi , Jason Luke Pereira , Sharu Theresa Jose , Osvaldo Simeone

Extracting information efficiently from quantum systems is a major component of quantum information processing tasks. Randomized measurements, or classical shadows, enable predicting many properties of arbitrary quantum states using few…

In reinforcement learning, an agent interacts sequentially with an environment to maximize a reward, receiving only partial, probabilistic feedback. This creates a fundamental exploration-exploitation trade-off: the agent must explore to…

Quantum Physics · Physics 2026-03-27 Josep Lumbreras , Ruo Cheng Huang , Yanglin Hu , Marco Fanizza , Mile Gu

Non-Markovian quantum processes exhibit different memory effects when measured in different ways; an unambiguous characterization of memory length requires accounting for the sequence of instruments applied to probe the system dynamics.…

Quantum Physics · Physics 2019-04-11 Philip Taranto , Simon Milz , Felix A. Pollock , Kavan Modi

A fundamental task in quantum information science is to measure nonlinear functionals of quantum states, such as $\mathrm{Tr}(\rho^k O)$. Intuitively, one expects that computing a $k$-th order quantity generally requires $O(k)$ copies of…

Quantum Physics · Physics 2025-09-03 Yukun Zhang , Yusen Wu , You Zhou , Xiao Yuan

Without large quantum computers to empirically evaluate performance, theoretical frameworks such as the quantum statistical query (QSQ) are a primary tool to study quantum algorithms for learning classical functions and search for quantum…

Quantum Physics · Physics 2026-02-11 Laura Lewis , Dar Gilboa , Jarrod R. McClean