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The one-clean qubit model (or the DQC1 model) is a restricted model of quantum computing where only a single qubit of the initial state is pure and others are maximally mixed. Although the model is not universal, it can efficiently solve…

Quantum Physics · Physics 2017-05-03 Tomoyuki Morimae , Keisuke Fujii , Harumichi Nishimura

The computational complexity of a quantum state quantifies how hard it is to make. `Complexity geometry', first proposed by Nielsen, is an approach to defining computational complexity using the tools of differential geometry. Here we…

High Energy Physics - Theory · Physics 2021-04-01 Adam R. Brown , Leonard Susskind

Quantum computation offers a promising new kind of information processing, where the non-classical features of quantum mechanics can be harnessed and exploited. A number of models of quantum computation exist, including the now well-studied…

Quantum Physics · Physics 2011-08-03 H. J. Briegel , D. E. Browne , W. Dür , R. Raussendorf , M. Van den Nest

We apply the recently developed notion of complexity for field theory to a quantum quench through a critical point in 1+1 dimensions. We begin with a toy model consisting of a quantum harmonic oscillator, and show that complexity exhibits…

High Energy Physics - Theory · Physics 2019-03-06 Hugo A. Camargo , Pawel Caputa , Diptarka Das , Michal P. Heller , Ro Jefferson

In standard quantum computation, the initial state is pure and the answer is determined by making a measurement of some of the bits in the computational basis. What can be accomplished if the initial state is a highly mixed state and the…

Quantum Physics · Physics 2009-01-23 E. Knill , R. Laflamme

We study the build up of complexity on the example of 1 kg matter in different forms. We start on the simplest example of ideal gases, and then continue with more complex chemical, biological, life and social and technical structures. We…

Other Quantitative Biology · Quantitative Biology 2017-01-19 L. P. Csernai , S. F. Spinnangr , S. Velle

We study approximation of embeddings between finite dimensional L_p spaces in the quantum model of computation. For the quantum query complexity of this problem matching (up to logarithmic factors) upper and lower bounds are obtained. The…

Quantum Physics · Physics 2007-05-23 Stefan Heinrich

While quantum speed-up in solving certain decision problems by a fault-tolerant universal quantum computer has been promised, a timely research interest includes how far one can reduce the resource requirement to demonstrate a provable…

Quantum Physics · Physics 2018-01-01 Jacob Miller , Stephen Sanders , Akimasa Miyake

Standard particle theory is based on quantized matter embedded in a classical geometry. Here, a complementary model is proposed, based on classical matter -- massive bodies, without quantum properties -- embedded in a quantum geometry. It…

Quantum Physics · Physics 2013-03-26 Craig Hogan

The complexity of quantum computation remains poorly understood. While physicists attempt to find ways to create quantum computers, we still do not have much evidence one way or the other as to how useful these machines will be. The tools…

Quantum Physics · Physics 2007-05-23 Lance Fortnow

For quantum many-body systems in one dimension, computational complexity theory reveals that the evaluation of ground-state energy remains elusive on quantum computers, contrasting the existence of a classical algorithm for temperatures…

Statistical Mechanics · Physics 2024-06-11 Atsushi Iwaki , Chisa Hotta

We define a semantic complexity class based on the model of quantum computing with just one pure qubit (as introduced by Knill and Laflamme) and discuss its computational power in terms of the problem of estimating the trace of a large…

Quantum Physics · Physics 2007-05-23 Dan Shepherd

Quantum bits can be isolated to perform useful information-theoretic tasks, even though physical systems are fundamentally described by very high-dimensional operator algebras. This is because qubits can be consistently embedded into…

Quantum Physics · Physics 2023-10-04 Andrew J. P. Garner , Markus P. Mueller

Superposition is the core feature that sets quantum theory apart from classical physics. Here, we investigate whether sets of quantum measurements can be modelled by using only devices that are operationally classical, in the sense that…

Quantum Physics · Physics 2026-03-30 Gabriele Cobucci , Alexander Bernal , Roope Uola , Armin Tavakoli

We will find a lower bound on the recognition complexity of the theories that are nontrivial relative to some equivalence relation (this relation may be equality), namely, each of these theories is consistent with the formula, whose sense…

Logic · Mathematics 2023-10-16 Ivan V. Latkin

We give new evidence that quantum computers -- moreover, rudimentary quantum computers built entirely out of linear-optical elements -- cannot be efficiently simulated by classical computers. In particular, we define a model of computation…

Quantum Physics · Physics 2010-11-16 Scott Aaronson , Alex Arkhipov

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

We discuss a classical complexity of finite-dimensional unitary transformations, which can been seen as a computable approximation of classical descriptional complexity of a unitary transformation acting on a set of qubits.

Quantum Physics · Physics 2023-04-03 Alexei Kaltchenko

A software product line models the variability of highly configurable systems. Complete exploration of all valid configurations (the configuration space) is infeasible as it grows exponentially with the number of features in the worst case.…

Quantum Physics · Physics 2023-07-28 Joshua Ammermann , Tim Bittner , Domenik Eichhorn , Ina Schaefer , Christoph Seidl

The one clean qubit model (or the DQC1 model) is a restricted model of quantum computing where only a single input qubit is pure and all other input qubits are maximally mixed. In spite of the severe restriction, the model can solve several…

Quantum Physics · Physics 2017-10-19 Tomoyuki Morimae