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The hopes for scalable quantum computing rely on the "threshold theorem": once the error per qubit per gate is below a certain value, the methods of quantum error correction allow indefinitely long quantum computations. The proof is based…

Quantum Physics · Physics 2014-01-17 M. I. Dyakonov

A universal set of gates for (classical or quantum) computation is a set of gates that can be used to approximate any other operation. It is well known that a universal set for classical computation augmented with the Hadamard gate results…

Quantum Physics · Physics 2022-02-11 Sebastian Horvat , Xiaoqin Gao , Borivoje Dakić

From the existence of an efficient quantum algorithm for factoring, it is likely that quantum computation is intrinsically more powerful than classical computation. At present, the best upper bound known for the power of quantum computation…

Quantum Physics · Physics 2015-09-14 Ciarán M. Lee , Jonathan Barrett

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

Quantum computation can be performed by encoding logical qubits into the states of two or more physical qubits, and controlling a single effective exchange interaction and possibly a global magnetic field. This "encoded universality"…

Quantum Physics · Physics 2007-05-23 M. Mohseni , D. A. Lidar

We obtain the first nontrivial time-space lower bound for quantum algorithms solving problems related to satisfiability. Our bound applies to MajSAT and MajMajSAT, which are complete problems for the first and second levels of the counting…

Quantum Physics · Physics 2007-12-18 Dieter van Melkebeek , Thomas Watson

This Letter discusses topological quantum computation with gapped boundaries of two-dimensional topological phases. Systematic methods are presented to encode quantum information topologically using gapped boundaries, and to perform…

Quantum Physics · Physics 2017-11-08 Iris Cong , Meng Cheng , Zhenghan Wang

Measurement-based quantum computation (MBQC) is a universal platform to realize unitary gates, only using measurements which act on a pre-prepared entangled resource state. By deforming the measurement bases, as well as the geometry of the…

Quantum Physics · Physics 2024-12-31 Daniel Azses , Jonathan Ruhman , Eran Sela

Non-Hermitian (NH) quantum systems demonstrate striking differences from their Hermitian counterparts, leading to claims of NH advantage in areas ranging from metrology to entanglement generation. We show that in the context of quantum…

Quantum Physics · Physics 2026-04-14 Brian Barch , Daniel Lidar

We investigate the problem of factorization of large numbers on a quantum computer which we imagine to be realized within a linear ion trap. We derive upper bounds on the size of the numbers that can be factorized on such a quantum…

Quantum Physics · Physics 2009-10-30 M. B. Plenio , P. L. Knight

We consider a model of quantum computation using qubits where it is possible to measure whether a given pair are in a singlet (total spin $0$) or triplet (total spin $1$) state. The physical motivation is that we can do these measurements…

Quantum Physics · Physics 2021-09-30 Michael H. Freedman , Matthew B. Hastings , Modjtaba Shokrian Zini

Measurement-based quantum computation describes a scheme where entanglement of resource states is utilized to simulate arbitrary quantum gates via local measurements. Recent works suggest that symmetry-protected topologically non-trivial,…

Quantum Physics · Physics 2018-02-14 Yanzhu Chen , Abhishodh Prakash , Tzu-Chieh Wei

We prove that quantum computation is polynomially equivalent to classical probabilistic computation with an oracle for estimating the value of simple sums, quadratically signed weight enumerators. The problem of estimating these sums can be…

Quantum Physics · Physics 2007-05-23 E. Knill , R. Laflamme

Polynomial--time constant--space quantum Turing machines (QTMs) and logarithmic--space probabilistic Turing machines (PTMs) recognize uncountably many languages with bounded error (Say and Yakary\i lmaz 2014, arXiv:1411.7647). In this…

Computational Complexity · Computer Science 2016-08-02 Maksims Dimitrijevs , Abuzer Yakaryılmaz

Space complexity is a key field of study in theoretical computer science. In the quantum setting there are clear motivations to understand the power of space-restricted computation, as qubits are an especially precious and limited resource.…

A longstanding goal in quantum information science is to demonstrate quantum computations that cannot be feasibly reproduced on a classical computer. Such demonstrations mark major milestones: they showcase fine control over quantum systems…

Recently Shor showed how to perform fault tolerant quantum computation when the error probability is logarithmically small. We improve this bound and describe fault tolerant quantum computation when the error probability is smaller than…

Quantum Physics · Physics 2008-02-03 Dorit Aharonov , Michael Ben-Or

We construct a model of quantum metrology inspired by the computational model known as deterministic quantum computation with one quantum bit (DQC1). Using only one pure qubit together with $l$ fully-mixed qubits we obtain measurement…

Quantum Physics · Physics 2016-04-22 Hugo Cable , Mile Gu , Kavan Modi

Measurement incompatibility stipulates the existence of quantum measurements that cannot be carried out simultaneously on single systems. We show that the set of input-output probabilities obtained from d-dimensional classical systems…

Quantum Physics · Physics 2023-06-13 Debashis Saha , Debarshi Das , Arun Kumar Das , Bihalan Bhattacharya , A. S. Majumdar

The Measurement Based Quantum Computation (MBQC) model achieves universal quantum computation by employing projective single qubit measurements with classical feedforward on a highly entangled multipartite cluster state. Rapid advances in…

Quantum Physics · Physics 2021-12-23 Swapnil Nitin Shah