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We show that any quantum algorithm searching an ordered list of n elements needs to examine at least 1/12 log n-O(1) of them. Classically, log n queries are both necessary and sufficient. This shows that quantum algorithms can achieve only…

Quantum Physics · Physics 2007-05-23 Andris Ambainis

In recent years, many computational tasks have been proposed as candidates for showing a quantum computational advantage, that is an advantage in the time needed to perform the task using a quantum instead of a classical machine.…

Quantum Physics · Physics 2021-02-12 Federico Centrone , Niraj Kumar , Eleni Diamanti , Iordanis Kerenidis

A digital computer is generally believed to be an efficient universal computing device; that is, it is believed able to simulate any physical computing device with an increase in computation time of at most a polynomial factor. This may not…

Quantum Physics · Physics 2017-02-20 Peter W. Shor

Quantum advantage is notoriously hard to find and even harder to prove. For example the class of functions computable with classical physics actually exactly coincides with the class computable quantum-mechanically. It is strongly believed,…

Quantum Physics · Physics 2015-10-07 Howard Dale , David Jennings , Terry Rudolph

One of the key challenges in quantum machine learning is finding relevant machine learning tasks with a provable quantum advantage. A natural candidate for this is learning unknown Hamiltonian dynamics. Here, we tackle the supervised…

Quantum Physics · Physics 2025-06-23 Alice Barthe , Mahtab Yaghubi Rad , Michele Grossi , Vedran Dunjko

It is usually assumed that a quantum computation is performed by applying gates in a specific order. One can relax this assumption by allowing a control quantum system to switch the order in which the gates are applied. This provides a more…

Quantum Physics · Physics 2020-06-11 Mateus Araújo , Fabio Costa , Časlav Brukner

We study space and time efficient quantum algorithms for two graph problems -- deciding whether an $n$-vertex graph is a forest, and whether it is bipartite. Via a reduction to the s-t connectivity problem, we describe quantum algorithms…

Quantum Physics · Physics 2016-10-04 Chris Cade , Ashley Montanaro , Aleksandrs Belovs

Fast algorithms for integer and polynomial multiplication play an important role in scientific computing as well as in other disciplines. In 1971, Sch{\"o}nhage and Strassen designed an algorithm that improved the multiplication time for…

Symbolic Computation · Computer Science 2018-11-06 Sviatoslav Covanov , Davood Mohajerani , Marc Moreno-Maza , Lin-Xiao Wang

Bosonic quantum systems operate in an infinite-dimensional Hilbert space, unlike discrete-variable quantum systems. This distinct mathematical structure leads to fundamental differences in quantum information processing, such as an…

Quantum Physics · Physics 2025-09-05 Varun Upreti , Dorian Rudolph , Ulysse Chabaud

This paper investigates the power of polynomial-time quantum computation in which only a very limited number of qubits are initially clean in the |0> state, and all the remaining qubits are initially in the totally mixed state. No…

Computational fluid dynamics (CFD) is a cornerstone of classical scientific computing, and there is growing interest in whether quantum computers can accelerate such simulations. To date, the existing proposals for fault-tolerant quantum…

Chain of thought is a natural inference-time method for increasing the computational power of transformer-based large language models (LLMs), but comes at the cost of sequential decoding. Are there more efficient alternatives to expand a…

Machine Learning · Computer Science 2025-11-07 William Merrill , Ashish Sabharwal

Quantum computer, harnessing quantum superposition to boost a parallel computational power, promises to outperform its classical counterparts and offer an exponentially increased scaling. The term "quantum advantage" was proposed to mark…

We develop a framework for learning from noisy quantum experiments in which fault-tolerant devices access uncharacterized systems through noisy couplings. Introducing the complexity class $\textsf{NBQP}$ ("noisy BQP''), we model noisy…

Quantum Physics · Physics 2026-01-15 Jordan Cotler , Weiyuan Gong , Ishaan Kannan

The hidden subgroup problem~(HSP) is one of the most important problems in quantum computation. Many problems for which quantum algorithm achieves exponential speedup over its classical counterparts can be reduced to the Abelian HSP.…

Quantum Physics · Physics 2023-05-05 Hefeng Wang

A key issue of current quantum advantage experiments is that their verification requires a full classical simulation of the ideal computation. This limits the regime in which the experiments can be verified to precisely the regime in which…

Quantum Physics · Physics 2025-10-08 Abhinav Deshpande , Bill Fefferman , Soumik Ghosh , Michael Gullans , Dominik Hangleiter

Quantum advantage, benchmarking the computational power of quantum machines outperforming all classical computers in a specific task, represents a crucial milestone in developing quantum computers and has been driving different physical…

We revisit the problem of characterising the complexity of Quantum PAC learning, as introduced by Bshouty and Jackson [SIAM J. Comput. 1998, 28, 1136-1153]. Several quantum advantages have been demonstrated in this setting, however, none…

Quantum Physics · Physics 2023-09-21 Wilfred Salmon , Sergii Strelchuk , Tom Gur

We establish connections between state tomography, pseudorandomness, quantum state synthesis, and circuit lower bounds. In particular, let $\mathfrak{C}$ be a family of non-uniform quantum circuits of polynomial size and suppose that there…

Quantum Physics · Physics 2025-09-26 Nai-Hui Chia , Daniel Liang , Fang Song

Classic cache-oblivious parallel matrix multiplication algorithms achieve optimality either in time or space, but not both, which promotes lots of research on the best possible balance or tradeoff of such algorithms. We study modern…

Distributed, Parallel, and Cluster Computing · Computer Science 2019-11-14 Yuan Tang