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The information obtained from the operation of a quantum gate on only two complementary sets of input states is sufficient to estimate the quantum process fidelity of the gate. In the case of entangling gates, these conditions can be used…

Quantum Physics · Physics 2017-08-23 Holger F. Hofmann , Ryo Okamoto , Shigeki Takeuchi

We propose a theoretical protocol to implement multiqubit geometric gates (i.e., the M{\o}lmer-S{\o}rensen gate) using photonic cat-state qubits. These cat-state qubits stored in high-$Q$ resonators are promising for hardware-efficient…

Quantum Physics · Physics 2022-09-05 Ye-Hong Chen , Roberto Stassi , Wei Qin , Adam Miranowicz , Franco Nori

We demonstrate laser-driven two-qubit and single-qubit logic gates with fidelities 99.9(1)% and 99.9934(3)% respectively, significantly above the approximately 99% minimum threshold level required for fault-tolerant quantum computation,…

Quantum Physics · Physics 2016-08-08 C. J. Ballance , T. P. Harty , N. M. Linke , M. A. Sepiol , D. M. Lucas

We study the speed/fidelity trade-off for a two-qubit phase gate implemented in $^{43}$Ca$^+$ hyperfine trapped-ion qubits. We characterize various error sources contributing to the measured fidelity, allowing us to account for errors due…

Quantum Physics · Physics 2016-08-10 C. J. Ballance , T. P. Harty , N. M. Linke , D. M. Lucas

The ability to generate and verify multipartite entanglement is an important benchmark for near-term quantum devices devices. We develop a scalable entanglement metric based on multiple quantum coherences, and demonstrate experimentally on…

Metastable atomic qubits are a highly promising platform for the realization of quantum computers, owing to their scalability and the possibility of converting leakage errors to erasure errors mid-circuit. Here, we demonstrate and…

High-fidelity two-qubit gates are essential for scalable quantum computing. We present a scheme based on superconducting transmon qubits and a control pulse delivery protocol that enables arbitrary controlled-phase gates modulated solely by…

We propose and analyse a scheme for performing a long-range entangling gate for qubits encoded in electron spins trapped in semiconductor quantum dots. Our coupling makes use of an electrostatic interaction between the state-dependent…

Mesoscale and Nanoscale Physics · Physics 2017-09-07 Samuel J. Elman , Stephen D. Bartlett , Andrew C. Doherty

A key challenge for semiconductor quantum-dot charge qubits is the realization of long-range qubit coupling and performing high-fidelity gates based on it. Here, we describe a new type of charge qubit formed by an electron confined in a…

Quantum Physics · Physics 2022-09-13 Chengxian Zhang , Guo Xuan Chan , Xin Wang , Zheng-Yuan Xue

We demonstrate that in a coupled two-qubit system any single-qubit gate can be decomposed into two conditional two-qubit gates and that any conditional two-qubit gate can be implemented by a manipulation analogous to that used for a…

Quantum Physics · Physics 2009-11-11 Zhongyuan Zhou , Shih-I Chu , Siyuan Han

Benchmarking large-scale quantum gates, typically involving multiple native two-qubit and singlequbit gates, is crucial in quantum computing. Global fidelity, encompassing information about intergate correlations, offers a comprehensive…

Fault-tolerant quantum computers which can solve hard problems rely on quantum error correction. One of the most promising error correction codes is the surface code, which requires universal gate fidelities exceeding the error correction…

Estimating the fidelity of state preparation in multi-qubit systems is generally a time-consuming task. Nevertheless, this complexity can be reduced if the desired state can be characterized by certain symmetries measurable with the…

Quantum Physics · Physics 2009-11-13 R. D. Somma , J. Chiaverini , D. J. Berkeland

Cat-state qubits (qubits encoded with cat states) have recently drawn intensive attention due to their enhanced life times with quantum error correction. We here propose a method to implement a universal controlled-phase gate of two…

Quantum Physics · Physics 2017-11-22 Yu Zhang , Xiong Zhao , Li Yu , Qi-Ping Su , Chui-Ping Yang

Today's most advanced ion trap quantum computers have significant overhead due to the need for dual-species operation. Looking ahead, logical qubit register sizes will be limited by the encoding rate needed to correct generic Pauli errors.…

We propose a realistic setup, inspired by already existing experiments, within which we develop a general formalism for the implementation of distributed quantum gates. Mediated by a quantum link that establishes a bidirectional quantum…

Entanglement is one of the key resources required for quantum computation, so experimentally creating and measuring entangled states is of crucial importance in the various physical implementations of a quantum computer. In superconducting…

The central challenge of quantum computing is implementing high-fidelity quantum gates at scale. However, many existing approaches to qubit control suffer from a scale-performance trade-off, impeding progress towards the creation of useful…

Superconducting circuits with coupler architecture receive considerable attention due to their advantages in tunability and scalability. Although single-qubit gates with low error have been achieved, high-fidelity two-qubit gates in coupler…

Quantum Physics · Physics 2021-05-28 Lijing Jin