Implementing the Quantum von Neumann Architecture with Superconducting Circuits

TLDR

The von Neumann architecture for a classical computer comprises a central processing unit and a memory holding instructions and data. We demonstrate a quantum central processing unit that exchanges data with a quantum random‑access memory integrated on a chip, with instructions stored on a classical computer. We test our quantum machine by executing codes that involve seven quantum elements: two superconducting qubits coupled through a quantum bus, two quantum memories, and two zeroing registers. We demonstrate the quantum Fourier transform with 66 % process fidelity and a three‑qubit Toffoli‑class OR phase gate with 98 % phase fidelity, and show that, with longer qubit coherence, this approach could enable factoring and simple quantum error correction.

Abstract

The von Neumann architecture for a classical computer comprises a central processing unit and a memory holding instructions and data. We demonstrate a quantum central processing unit that exchanges data with a quantum random-access memory integrated on a chip, with instructions stored on a classical computer. We test our quantum machine by executing codes that involve seven quantum elements: Two superconducting qubits coupled through a quantum bus, two quantum memories, and two zeroing registers. Two vital algorithms for quantum computing are demonstrated, the quantum Fourier transform, with 66% process fidelity, and the three-qubit Toffoli-class OR phase gate, with 98% phase fidelity. Our results, in combination especially with longer qubit coherence, illustrate a potentially viable approach to factoring numbers and implementing simple quantum error correction codes.