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Modeling non-Hermitian Hamiltonians is increasingly important in classical and quantum domains, especially when studying open systems, $PT$ symmetry, and resonances. However, the quantum simulation of these models has been limited by the…

Quantum Physics · Physics 2025-02-20 Anastashia Jebraeilli , Michael R. Geller

Current quantum computing hardware is restricted by the availability of only few, noisy qubits which limits the investigation of larger, more complex molecules in quantum chemistry calculations on quantum computers in the near-term. In this…

It is often said that the transition from quantum to classical worlds is caused by decoherence originated from an interaction between a system of interest and its surrounding environment. Here we establish a computational quantum-classical…

Quantum Physics · Physics 2016-04-08 Keisuke Fujii , Shuhei Tamate

Quantum circuits that are classically simulatable tell us when quantum computation becomes less powerful than or equivalent to classical computation. Such classically simulatable circuits are of importance because they illustrate what makes…

Quantum Physics · Physics 2022-01-26 Ryotaro Suzuki , Kosuke Mitarai , Keisuke Fujii

The Swap gate is a ubiquitous tool for moving information on quantum hardware, yet it can be considered a classical operation because it does not entangle product states. Genuinely quantum operations could outperform Swap for the task of…

Quantum Physics · Physics 2023-02-02 Aniruddha Bapat , Andrew M. Childs , Alexey V. Gorshkov , Eddie Schoute

(Abridged.) Quantum computers promise to solve some problems exponentially faster than traditional computers, but we still do not fully understand why this is the case. While the most studied model of quantum computation uses qubits, which…

Quantum Physics · Physics 2025-05-29 Cameron Calcluth

It is one of the most fundamental objectives in quantum information science to understand the boundary between the computational power of classical and quantum computers. One possible avenue to explore this boundary is to identify classes…

Quantum Physics · Physics 2025-03-28 Christophe Piveteau

We study the classical simulability of a polynomial-size quantum circuit $C_n$ on $n$ qubits followed by sparse classical post-processing (SCP) on $m$ bits, where $m \leq n \leq {\rm poly}(m)$. The SCP is described by a non-zero Boolean…

Quantum Physics · Physics 2026-03-09 Yasuhiro Takahashi , Masayuki Miyamoto , Noboru Kunihiro

Magic states are essential for universal quantum computation and are widely viewed as a key source of quantum advantage, yet in realistic devices they are inevitably noisy. In this work, we characterize how noise on injected magic resources…

Quantum Physics · Physics 2026-01-21 Jiwon Heo , Sojeong Park , Changhun Oh

Quantum computing has potential to provide exponential speedups over classical computing for many important applications. However, today's quantum computers are in their early stages, and hardware quality issues hinder the scale of program…

We show that several quantum circuit families can be simulated efficiently classically if it is promised that their output distribution is approximately sparse i.e. the distribution is close to one where only a polynomially small, a priori…

Quantum Physics · Physics 2013-10-28 Martin Schwarz , Maarten Van den Nest

We study the effect of noise on the classical simulatability of quantum circuits defined by computationally tractable (CT) states and efficiently computable sparse (ECS) operations. Examples of such circuits, which we call CT-ECS circuits,…

Quantum Physics · Physics 2020-08-28 Yasuhiro Takahashi , Yuki Takeuchi , Seiichiro Tani

Clifford circuits -- i.e. circuits composed of only CNOT, Hadamard, and $\pi/4$ phase gates -- play a central role in the study of quantum computation. However, their computational power is limited: a well-known result of Gottesman and…

Quantum Physics · Physics 2018-06-21 Adam Bouland , Joseph F. Fitzsimons , Dax Enshan Koh

Quantum simulations consist in the intentional reproduction of physical or unphysical models into another more controllable quantum system. Beyond establishing communication vessels between unconnected fields, they promise to solve complex…

Quantum Physics · Physics 2018-04-24 Lucas Lamata , Adrian Parra-Rodriguez , Mikel Sanz , Enrique Solano

Quantum computing (QC) offers a new computing paradigm that has the potential to provide significant speedups over classical computing. Each additional qubit doubles the size of the computational state space available to a quantum…

Quantum Physics · Physics 2022-05-13 Wei Tang , Margaret Martonosi

Quantum computation has attracted much attention, among other things, due to its potentialities to solve classical NP problems in polynomial time. For this reason, there has been a growing interest to build a quantum computer. One of the…

Quantum Physics · Physics 2007-05-23 P. B. M. Sousa , R. V. Ramos

The Gottesman-Knill theorem asserts that quantum circuits composed solely of Clifford gates can be efficiently simulated classically. This theorem hinges on the fact that Clifford gates map Pauli strings to other Pauli strings, thereby…

Quantum Physics · Physics 2024-07-30 George Biswas

The task of learning a probability distribution from samples is ubiquitous across the natural sciences. The output distributions of local quantum circuits form a particularly interesting class of distributions, of key importance both to…

In this paper, we propose quantum circuits for runtime assertions, which can be used for both software debugging and error detection. Runtime assertion is challenging in quantum computing for two key reasons. First, a quantum bit (qubit)…

Quantum Physics · Physics 2019-10-23 Huiyang Zhou , Gregory Byrd

We employ quantum circuit learning to simulate quantum field theories (QFTs). Typically, when simulating QFTs with quantum computers, we encounter significant challenges due to the technical limitations of quantum devices when implementing…

High Energy Physics - Theory · Physics 2025-04-08 Kazuki Ikeda