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arXiv · 2211.09060

All-optical quantum computing using cubic phase gates

Niklas Budinger·Akira Furusawa·Peter van Loock
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Abstract

If suitable quantum optical interactions were available, transforming optical field mode operators in a nonlinear fashion, the all-photonics platform could be one of the strongest contenders for realizing a quantum computer. Unlike other, matter-based (solid-state or atomic) platforms, photonic qubits can be operated at room temperature and high clock rates (GHz or, in principle, even THz). In addition, recent continuous-variable time-domain approaches are extremely well scalable. Moreover, while single-photon qubits may be processed directly, "brighter" logical qubits may be embedded in individual oscillator modes, using so-called bosonic codes, for an in-principle fault-tolerant processing. In this paper, we show how elements of all-optical, universal, and fault-tolerant quantum computation can be implemented using only beam splitters together with single-mode cubic phase gates in reasonable numbers, and possibly off-line squeezed-state or single-photon resources. Our approach is based on a decomposition technique combining exact gate decompositions and approximate Trotterization. This allows for efficient decompositions of certain nonlinear continuous-variable multimode gates into the elementary gates, where the few cubic gates needed may even be weak or all identical, thus facilitating potential experiments. The final gate operations include two-mode controlled phase rotation and three-mode Rabi-type Hamiltonian gates, which are shown to be employable for realizing high-fidelity single-photon two-qubit entangling gates or, as a bosonic-code example, creating high-quality Gottesman-Kitaev-Preskill states. We expect our method of general use with various applications, including those that rely on quartic Kerr-type interactions.

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Niklas Budinger, Akira Furusawa, Peter van Loock. 2024-07-13. All-optical quantum computing using cubic phase gates. https://doi.org/10.1103/physrevresearch.6.023332

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