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By harnessing the superposition and entanglement of physical states, quantum computers could outperform their classical counterparts in solving problems of technological impact, such as factoring large numbers and searching databases. A…

Mesoscale and Nanoscale Physics · Physics 2009-07-09 L. DiCarlo , J. M. Chow , J. M. Gambetta , Lev S. Bishop , B. R. Johnson , D. I. Schuster , J. Majer , A. Blais , L. Frunzio , S. M. Girvin , R. J. Schoelkopf

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

Coupled Kerr parametric oscillators (KPOs) are a promising resource for classical and quantum analog computation, for example to find the ground state of Ising Hamiltonians. Yet, the state space of strongly coupled KPO networks is very…

Classical Physics · Physics 2025-11-18 Gabriel Margiani , Orjan Ameye , Oded Zilberberg , Alexander Eichler

Near-term quantum computers are limited by the decoherence of qubits to only being able to run low-depth quantum circuits with acceptable fidelity. This severely restricts what quantum algorithms can be compiled and implemented on such…

A two-qubit quantum gate is realized using electronic excited states in a single ion with an energy separation on the order of a terahertz times the Planck constant as a qubit. Two phase locked lasers are used to excite a stimulated Raman…

Quantum Physics · Physics 2015-05-18 K. Toyoda , S. Haze , R. Yamazaki , S. Urabe

We propose a universal gate set for quantum computing with all-to-all connectivity and intrinsic robustness to bit-flip errors based on parity encoding. We show that logical controlled phase gate and $R_z$ rotations can be implemented in…

Quantum Physics · Physics 2022-11-03 Michael Fellner , Anette Messinger , Kilian Ender , Wolfgang Lechner

Quantum computers based on silicon are promising candidates for long term universal quantum computation due to the long coherence times of electron and nuclear spin states. Furthermore, the continuous progress of micro- and nano-…

Quantum Physics · Physics 2022-03-23 Davide Rei , Elena Ferraro , Marco De Michielis

Since the first demonstration of coherent control of a quantum state of a superconducting charge qubit a variety of Josephson-junction-based qubits have been implemented with remarkable progress in coherence time and read-out schemes.…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 T. Yamamoto , Yu. A. Pashkin , O. Astafiev , Y. Nakamura , J. S. Tsai

Increasing quantum circuit fidelity requires an efficient instruction set to avoid errors from decoherence. The choice of a two-qubit (2Q) hardware basis gate depends on a quantum modulator's native Hamiltonian interactions and applied…

Quantum Physics · Physics 2025-04-22 Evan McKinney , Chao Zhou , Mingkang Xia , Michael Hatridge , Alex K. Jones

Quantum circuits currently constitute a dominant model for quantum computation. Our work addresses the problem of constructing quantum circuits to implement an arbitrary given quantum computation, in the special case of two qubits. We…

Quantum Physics · Physics 2009-11-07 Stephen S. Bullock , Igor L. Markov

Optimal implementation of quantum gates is crucial for designing a quantum computer. The necessary condition for optimal construction of a two-qubit unitary operation is obtained. It can be proved that the B gate is the unique gate that can…

Quantum Physics · Physics 2009-11-10 Yong-Sheng Zhang , Ming-Yong Ye , Guang-Can Guo

We demonstrate that conditional as well as unconditional basic operations which are prerequisite for universal quantum gates can be performed with almost 100% fidelity within a strongly interacting two-electron quantum ring. Both sets of…

Mesoscale and Nanoscale Physics · Physics 2016-08-14 Lene Sælen , Erik Waltersson , J. P. Hansen , Eva Lindroth

Quantum superpositions of macroscopically distinct classical states, so-called Schr\"{o}dinger cat states, are a resource for quantum metrology, quantum communication, and quantum computation. In particular, the superpositions of two…

We theoretically propose a method for on-demand generation of traveling Schr\"odinger cat states, namely, quantum superpositions of distinct coherent states of traveling fields. This method is based on deterministic generation of…

Quantum Physics · Physics 2019-02-27 Hayato Goto , Zhirong Lin , Tsuyoshi Yamamoto , Yasunobu Nakamura

Cat states of the microwave field stored in high-Q resonators show great promise for robust encoding and manipulation of quantum information. Here we propose an approach to efficiently prepare such cat states in a Kerr-nonlinear resonator…

Quantum Physics · Physics 2017-04-24 Shruti Puri , Samuel Boutin , Alexandre Blais

The Kerr-cat qubit is a bosonic qubit in which multi-photon Schrodinger cat states are stabilized by applying a two-photon drive to an oscillator with a Kerr nonlinearity. The suppressed bit-flip rate with increasing cat size makes this…

A proof is given, which relies on the commutator algebra of the unitary Lie groups, that quantum gates operating on just two bits at a time are sufficient to construct a general quantum circuit. The best previous result had shown the…

Condensed Matter · Physics 2009-10-22 David P. Divincenzo

High-fidelity single- and two-qubit gates are essential building blocks for a fault-tolerant quantum computer. While there has been much progress in suppressing single-qubit gate errors in superconducting qubit systems, two-qubit gates…

Universal quantum computation requires high fidelity single qubit rotations and controlled two qubit gates. Along with high fidelity single qubit gates, strong efforts have been made in developing robust two qubit logic gates in…

Mesoscale and Nanoscale Physics · Physics 2016-10-20 D. R. Ward , Dohun Kim , D. E. Savage , M. G. Lagally , R. H. Foote , Mark Friesen , S. N. Coppersmith , Mark A. Eriksson

Robust quantum computation with d-level quantum systems (qudits) poses two requirements: fast, parallel quantum gates and high fidelity two-qudit gates. We first describe how to implement parallel single qudit operations. It is by now well…

Quantum Physics · Physics 2009-11-13 Dianne P. O'Leary , Gavin K. Brennen , Stephen S. Bullock