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We have neglected here the weak induced anharmonicity of the cavity modes. Superconducting Circuits: Hamiltonians by Design Unlike microscopic entities-electrons, atoms, ions, and photons-on which other qubits are based, superconducting quantum circuits are based on the electrical (LC) oscillator ( When several of these qubits, which are nonlinear oscillators behaving as artificial atoms, are coupled to true oscillators (photons in a microwave cavity), one obtains, for low-lying excitations, an effective multiqubit, multicavity system Hamiltonian of the form can perform arbitrary quantum operations at speeds determined by the nonlinear interaction strengths and , typically 43,44 resulting in single-qubit gate times within 5 to 50 ns (/2 ≈ 200 MHz) and two qubit entangling gate times within 50 to 500 ns (/2 ≈ 20 MHz). The final two stages in reaching the ultimate goal of faulttolerant quantum information processing 26 require the ability to do all single qubit operations on one logical qubit (which is an effective qubit protected by active error correction mechanisms), and the ability to perform gate operations between several logical qubits in both stages the enhanced coherence lifetime of the qubits should be preserved. This goal is as yet unfulfilled in any system.
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The invention of quantum error correction (QEC) Below, we discuss the specific physical implementation of general-purpose QIP with superconducting qubits Toward a Quantum Computer Developing a quantum computer involves several overlapping and interconnecting stages coherence time that is longer than any of the individual components. The concept of solving problems with the use of quantum algorithms, introduced in the early 1990s 1,2, was welcomed as a revolutionary change in the theory of computational complexity, but the feat of actually building a quantum computer was then thought to be impossible. We offer a view on some directions for the field and speculate on its future. For the first time, physicists will have to master quantum error correction to design and operate complex active systems that are dissipative in nature, yet remain coherent indefinitely. However, building an error-corrected information processor with many such qubits will require solving specific architecture problems that constitute a new field of research. These circuits benefit from the robustness of superconductivity and the Josephson effect, and at present they have not encountered any fundamental physical limits.
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The performance of superconducting qubits has improved by several orders of magnitude in the past decade.
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