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Continuously parameterized two-qubit gates are a key feature of state-of-the-art trapped-ion quantum processors as they have favorable error scalings and show distinct improvements in circuit performance over more restricted maximally…

This paper studies the problem of stabilizing a self-triggered control system with quantized output. Employing a standard observer-based state feedback control law, a self-triggering mechanism that dictates the next sampling time based on…

Systems and Control · Electrical Eng. & Systems 2023-02-15 Wenjie Liu , Masashi Wakaiki , Jian Sun , Gang Wang , Jie Chen

We introduce magic measures to quantify the nonstabilizerness of multiqubit quantum gates and establish lower bounds on the $T$ count for fault-tolerant quantum computation. First, we introduce the stabilizer nullity of multi-qubit unitary,…

Quantum Physics · Physics 2023-03-21 Jiaqing Jiang , Xin Wang

Quantum states obey an asymptotic no-cloning theorem, stating that no deterministic machine can reliably replicate generic sequences of identically prepared pure states. In stark contrast, we show that generic sequences of unitary gates can…

Quantum Physics · Physics 2015-04-01 G. Chiribella , Y. Yang , C. Huang

To achieve scalable quantum computing, improving entangling-gate fidelity and its implementation-efficiency are of utmost importance. We present here a linear method to construct provably power-optimal entangling gates on an arbitrary pair…

Quantum Physics · Physics 2021-08-10 Reinhold Blumel , Nikodem Grzesiak , Neal Pisenti , Kenneth Wright , Yunseong Nam

Quantum random number generators (QRNGs) promise perfectly unpredictable random numbers. However, the security certification of the random numbers in form of a stochastic model often introduces assumptions that are either hardly justified…

We study the stabilization of an unpredictable linear control system where the controller must act based on a rate-limited observation of the state. More precisely, we consider the system $X_{n+1} = A_n X_n + W_n - U_n$, where the $A_n$'s…

Systems and Control · Computer Science 2018-05-16 Victoria Kostina , Yuval Peres , Gireeja Ranade , Mark Sellke

Fault-tolerant quantum computation allows quantum computations to be carried out while resisting unwanted noise. Several error-correcting codes have been developed to achieve this task, but none alone are capable of universal quantum…

Quantum Physics · Physics 2026-04-29 Nicholas J. C. Papadopoulos , Ramin Ayanzadeh

In this work, we consider an environment formed by incoherent photons as a resource for controlling open quantum systems via an incoherent control. We exploit a coherent control in the Hamiltonian and an incoherent control in the dissipator…

Quantum Physics · Physics 2023-03-01 Vadim Petruhanov , Alexander Pechen

This paper aims to introduce a design methodology to stabilize a chain of integrators in a fixed-time with predefined Upper Bound for the Settling-Time (UBST). This approach is based on time-varying gains (time-base generator) that become…

Optimization and Control · Mathematics 2020-04-30 David Gómez-Gutiérrez

Quantum process tomography is a necessary tool for verifying quantum gates and diagnosing faults in architectures and gate design. We show that the standard approach of process tomography is grossly inaccurate in the case where the states…

We experimentally demonstrate a controlled-phase gate for continuous variables in a fully measurement-based fashion. In our scheme, the two independent input states of the gate, encoded in two optical modes, are teleported into a four-mode…

Quantum Physics · Physics 2012-01-30 Ryuji Ukai , Shota Yokoyama , Jun-ichi Yoshikawa , Peter van Loock , Akira Furusawa

Quantum states with nonlinear squeezing are a necessary resource for deterministic implementation of high-order quadrature phase gates that are, in turn, sufficient for advanced quantum information processing. We demonstrate that this class…

Quantum Physics · Physics 2021-07-15 Šimon Bräuer , Petr Marek

We apply a notion of static renormalization to the preparation of entangled states for quantum computing, exploiting ideas from percolation theory. Such a strategy yields a novel way to cope with the randomness of non-deterministic quantum…

Quantum Physics · Physics 2009-11-13 K. Kieling , T. Rudolph , J. Eisert

A quantum computer based on an asymmetric coupled dot system has been proposed and shown to operate as the controlled-NOT-gate. The basic idea is (1) the electron is localized in one of the asymmetric coupled dots. (2)The electron transfer…

Quantum Physics · Physics 2008-12-18 Tetsufumi Tanamoto

Long-range entangled states are vital for quantum information processing and quantum metrology. Preparing such states by combining measurements with unitary gates opened new possibilities for efficient protocols with finite-depth quantum…

Quantum Physics · Physics 2024-08-07 Iosifina Angelidi , Marcin Szyniszewski , Arijeet Pal

The leading paradigm for performing computation on quantum memories can be encapsulated as distill-then-synthesize. Initially, one performs several rounds of distillation to create high-fidelity magic states that provide one good T gate, an…

Quantum Physics · Physics 2017-02-15 Earl T. Campbell , Mark Howard

Quantum control plays an irreplaceable role in practical use of quantum computers. However, some challenges have to be overcome to find more suitable and diverse control parameters. We propose a promising and generalizable…

Quantum Physics · Physics 2023-09-29 Meng-Yun Mao , Zheng Cheng , Yan Xia , Andrzej M. Oleś , Wen-Long You

The challenge of quantum computing is to combine error resilience with universal computation. Diagonal gates such as the transversal $T$ gate play an important role in implementing a universal set of quantum operations. This paper…

Quantum Physics · Physics 2022-09-14 Jingzhen Hu , Qingzhong Liang , Robert Calderbank

A new method for controlling harmonic generation, in the framework of quantum optimal control theory (QOCT), is developed. The problem is formulated in the frequency domain using a new maximization functional. The relaxation method is used…

Quantum Physics · Physics 2012-08-28 Ido Schaefer