Abstract
Building a quantum computer is a daunting challenge since it requires good control but also good isolation from the environment to minimize decoherence. It is therefore important to realize quantum gates efficiently, using as few operations as possible, to reduce the amount of required control and operation time and thus improve the quantum state coherence. Here we propose a superconducting circuit for implementing a tunable system consisting of a qutrit coupled to two qubits. This system can efficiently accomplish various quantum information tasks, including generation of entanglement of the two qubits and conditional three-qubit quantum gates, such as the Toffoli and Fredkin gates. Furthermore, the system realizes a conditional geometric gate which may be used for holonomic (non-adiabatic) quantum computing. The efficiency, robustness and universality of the presented circuit makes it a promising candidate to serve as a building block for larger networks capable of performing involved quantum computational tasks.
Highlights
Richard Feynman famously suggested to simulate quantum physics with quantum computers[1]
Most implementations so far have used only one- and two-qubit quantum operations for realizing important multi-qubit gates[34] such as the three-qubit quantum Toffoli[35] and Fredkin[36] gates, requiring a theoretical minimum of five two-qubit gates[34,37,38]. This large number of required gates can be remedied by the use of a higher-lying state of a qutrit which can simplify the implementation of e.g. the Toffoli gate to three two-qubit gates as implemented optically in[39] and in superconducting circuits in[40]
We will show that this double-controlled gate can be used to implement the three-qubit Deutsch gate and is universal for quantum computing in itself, adding yet another tool in our toolbox for efficient quantum gates
Summary
Richard Feynman famously suggested to simulate quantum physics with quantum computers[1]. Most implementations so far have used only one- and two-qubit quantum operations for realizing important multi-qubit gates[34] such as the three-qubit quantum Toffoli[35] (ccnot) and Fredkin[36] (cswap) gates, requiring a theoretical minimum of five two-qubit gates[34,37,38]. This large number of required gates can be remedied by the use of a higher-lying state of a qutrit which can simplify the implementation of e.g. the Toffoli gate to three two-qubit gates as implemented optically in[39] and in superconducting circuits in[40]. We will show that this double-controlled gate can be used to implement the three-qubit Deutsch gate and is universal for quantum computing in itself, adding yet another tool in our toolbox for efficient quantum gates
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