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Complex quantum circuits are constituted by combinations of quantum subroutines. The computation is possible as long as the quantum data encoding is consistent throughout the circuit. Despite its fundamental importance, the formalization of…

Emerging Technologies · Computer Science 2025-11-10 Gabriele Agliardi , Enrico Prati

The "quantum complexity" of a unitary operator measures the difficulty of its construction from a set of elementary quantum gates. While the notion of quantum complexity was first introduced as a quantum generalization of the classical…

Quantum Physics · Physics 2021-11-02 Vir B. Bulchandani , S. L. Sondhi

Quantum circuits consisting of random unitary gates and subject to local measurements have been shown to undergo a phase transition, tuned by the rate of measurement, from a state with volume-law entanglement to an area-law state. From a…

Statistical Mechanics · Physics 2021-10-26 Yimu Bao , Soonwon Choi , Ehud Altman

Owing to the computational complexity of electronic structure algorithms running on classical digital computers, the range of molecular systems amenable to simulation remains tightly circumscribed even after many decades of work. Quantum…

Quantum Physics · Physics 2022-05-18 Alexis Ralli , Michael I. Williams , Peter V. Coveney

Quantum computers have now appeared in our society and are utilized for the investigation of science and engineering. At present, they have been built as intermediate-size computers containing about fifty qubits and are weak against noise…

Quantum Physics · Physics 2020-12-07 Yusuke Hama

In this work, we propose a generalization of the current most widely used quantum computing hardware metric known as the quantum volume. The quantum volume specifies a family of random test circuits defined such that the logical circuit…

Quantum Physics · Physics 2022-07-18 Keith Miller , Charles Broomfield , Ann Cox , Joe Kinast , Brandon Rodenburg

Quantum computational complexity estimates the difficulty of constructing quantum states from elementary operations, a problem of prime importance for quantum computation. Surprisingly, this quantity can also serve to study a completely…

High Energy Physics - Theory · Physics 2022-03-02 Shira Chapman , Giuseppe Policastro

According to quantum mechanics, the informational content of isolated systems does not change in time. However, subadditivity of entropy seems to describe an excess of information when we look at single parts of a composite systems and…

Quantum Physics · Physics 2019-11-12 Marco Roncaglia

We initiate the systematic study of experimental quantum physics from the perspective of computational complexity. To this end, we define the framework of quantum algorithmic measurements (QUALMs), a hybrid of black box quantum algorithms…

Quantum Physics · Physics 2022-03-09 Dorit Aharonov , Jordan Cotler , Xiao-Liang Qi

Quantum computers hold promise to enable efficient simulations of the properties of molecules and materials; however, at present they only permit ab initio calculations of a few atoms, due to a limited number of qubits. In order to harness…

Materials Science · Physics 2020-07-07 He Ma , Marco Govoni , Giulia Galli

Quantum measurement is a fundamental concept in the field of quantum mechanics. The action of quantum measurement, leading the superposition state of the measured quantum system into a definite output state, not only reconciles…

General Physics · Physics 2024-08-13 Wei Wen

Quantum computing is a promising paradigm that may overcome the current computational power bottlenecks. The increasing maturity of quantum processors provides more possibilities for the development and implementation of quantum algorithms.…

Quantum Physics · Physics 2025-10-15 Ge Yan , Wenjie Wu , Yuheng Chen , Kaisen Pan , Xudong Lu , Zixiang Zhou , Yuhan Wang , Ruocheng Wang , Junchi Yan

The execution of quantum circuits on real systems has largely been limited to those which are simply time-ordered sequences of unitary operations followed by a projective measurement. As hardware platforms for quantum computing continue to…

Quantum advantage schemes probe the boundary between classically simulatable and classically intractable quantum dynamics. We explore the impact of mid-circuit measurements on the computational power of quantum circuits. To this effect, we…

Quantum Physics · Physics 2026-03-24 Chenfeng Cao , Jens Eisert

Quantum computers can accurately compute ground state energies using phase estimation, but this requires a guiding state that has significant overlap with the true ground state. For large molecules and extended materials, it becomes…

This paper explores the problem of quantum measurement complexity. In computability theory, the complexity of a problem is determined by how long it takes an effective algorithm to solve it. This complexity may be compared to the difficulty…

Quantum Physics · Physics 2014-10-27 Subhash Kak

By exploiting the complexity intrinsic to quantum dynamics, quantum technologies promise a whole host of computational advantages. One such advantage lies in the field of stochastic modelling, where it has been shown that quantum stochastic…

Quantum Physics · Physics 2024-02-28 Thomas J. Elliott , Mile Gu

Quantum circuit complexity has played a central role in recent advances in holography and many-body physics. Within quantum field theory, it has typically been studied in a Lorentzian (real-time) framework. In a departure from standard…

High Energy Physics - Theory · Physics 2022-10-12 Josiah Couch , Yale Fan , Sanjit Shashi

Quantum chaos is presented as a paradigm of information processing by dynamical systems at the bottom of the range of phase-space scales. Starting with a brief review of classical chaos as entropy flow from micro- to macro-scales, I argue…

Quantum Physics · Physics 2019-05-01 Thomas Dittrich

Quantum simulation is a potentially powerful application of quantum computing, holding the promise to be able to emulate interesting quantum systems beyond the reach of classical computing methods. Despite such promising applications, and…

Quantum Physics · Physics 2022-10-07 Kaelyn J. Ferris , A. J. Rasmusson , Nicholas T. Bronn , Olivia Lanes