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Protecting information against decoherence in open quantum systems remains a central challenge for quantum computing. In particular, passive error correction schemes have so far been limited to static memories rather than dynamical qubits.…

Quantum Physics · Physics 2026-02-25 Mert Esencan , A. I. Lvovsky , Berislav Buča

We present novel algorithms to estimate outcomes for qubit quantum circuits. Notably, these methods can simulate a Clifford circuit in linear time without ever writing down stabilizer states explicitly. These algorithms outperform previous…

Quantum Physics · Physics 2019-07-03 Patrick Rall , Daniel Liang , Jeremy Cook , William Kretschmer

The study of the boundary between classically simulable and computationally complex quantum dynamics is fundamental to understanding which physical resources may enable enhanced information-processing capabilities. We investigate this…

Quantum Physics · Physics 2026-05-08 Moein N. Ivaki , Matias Karjula , Tapio Ala-Nissila

Fault-tolerant quantum computation (FTQC) schemes using large block codes that encode $k>1$ qubits in $n$ physical qubits can potentially reduce the resource overhead to a great extent because of their high encoding rate. However, the…

Quantum Physics · Physics 2020-08-04 Yi-Cong Zheng , Ching-Yi Lai , Todd A. Brun , Leong-Chuan Kwek

We propose hardware-efficient schemes for implementing logical H and S gates transversally on rotated surface codes with reconfigurable neutral atom arrays. For logical H gates, we develop a simple strategy to rotate code patches…

Quantum Physics · Physics 2024-12-03 Zi-Han Chen , Ming-Cheng Chen , Chao-Yang Lu , Jian-Wei Pan

The Toffoli gate is an important universal quantum gate, and will alongside the Clifford gates be available in future fault-tolerant quantum computing hardware. Many quantum algorithms rely on performing arbitrarily small single-qubit…

Quantum Physics · Physics 2026-03-13 Christoffer Hindlycke , Jakov Krnic , Jan-Åke Larsson

In a modern error corrected quantum memory or circuit, parallelization of gate operations is severely restricted due to issues like cross-talk. Hence, there are enough idle qubits not undergoing gate operations either during the computation…

Quantum Physics · Physics 2025-02-17 Sai Sanjay Narayanan , Smita Bagewadi , Avhishek Chatterjee

We implement a complete randomized benchmarking protocol on a system of two superconducting qubits. The protocol consists of randomizing over gates in the Clifford group, which experimentally are generated via an improved two-qubit…

We aim to establish a scalable scheme for characterising diagonal non-Clifford gates for single- and multi-qudit systems; \(d\) is a prime-power integer. By employing cyclic operators and a qudit T gate, we generalise the dihedral…

Quantum Physics · Physics 2024-08-02 David Amaro-Alcalá , Barry C. Sanders , Hubert de Guise

We give a protocol for the delegation of quantum computation on encrypted data. More specifically, we show that in a client-server scenario, where the client holds the encryption key for an encrypted quantum register held by the server, it…

Quantum Physics · Physics 2015-09-15 Anne Broadbent

Transversal gates are the ideal gates in a fault-tolerant scenario; relatively easy to implement, and minimally error propagating. Their availability will maximise fault tolerant thresholds, enabling universal quantum computation in a wider…

Quantum Physics · Physics 2025-06-23 Heather Leitch , Alastair Kay

A central task towards building a practical quantum computer is to protect individual qubits from decoherence while retaining the ability to perform high-fidelity entangling gates involving arbitrary two qubits. Here we propose and…

While the accuracy of qubit operations has been greatly improved in the last decade, further development is demanded to achieve the ultimate goal: a fault-tolerant quantum computer that can solve real-world problems more efficiently than…

Quantum Physics · Physics 2024-08-29 Kiyoto Nakamura , Joachim Ankerhold

Recent work of Bravyi et al. and follow-up work by Bene Watts et al. demonstrates a quantum advantage for shallow circuits: constant-depth quantum circuits can perform a task which constant-depth classical (i.e., AC$^0$) circuits cannot.…

Quantum Physics · Physics 2019-11-07 Daniel Grier , Luke Schaeffer

Fault-tolerant quantum computation requires minimizing non-Clifford gates, whose implementation via magic state distillation dominates the resource costs. While $T$-count minimization is well-studied, dedicated $CCZ$ factories shift the…

Quantum Physics · Physics 2026-02-18 Kirill Khoruzhii , Patrick Gelß , Sebastian Pokutta

The states needed in a quantum computation are extremely affected by decoherence. Several methods have been proposed to control error spreading. They use two main tools: fault-tolerant constructions and concatenated quantum error correcting…

Quantum Physics · Physics 2007-05-23 Pedro J. Salas , Angel L. Sanz

In this paper, we study the problem of learning an unknown quantum circuit of a certain structure. If the unknown target is an $n$-qubit Clifford circuit, we devise an efficient algorithm to reconstruct its circuit representation by using…

Quantum Physics · Physics 2022-06-29 Ching-Yi Lai , Hao-Chung Cheng

We study quantum networks with tree structures, in which information propagates from a root to leaves. At each node in the network, the received qubit unitarily interacts with fresh ancilla qubits, after which each qubit is sent through a…

Quantum Physics · Physics 2026-01-14 Shiv Akshar Yadavalli , Iman Marvian

Fault-tolerant quantum computing demands decoders that are fast, accurate, and adaptable to circuit structure and realistic noise. While machine learning (ML) decoders have demonstrated impressive performance for quantum memory, their use…

Quantum Physics · Physics 2025-09-16 J. Pablo Bonilla Ataides , Andi Gu , Susanne F. Yelin , Mikhail D. Lukin

Quantum teleportation channels can overcome the effects of photonic loss, a major challenge in the implementation of a quantum network over fiber. Teleportation channels are created by distributing an entangled state between two nodes which…

Quantum Physics · Physics 2022-05-16 Aparimit Chandra , Wenhan Dai , Don Towsley