Coherent coupled qubits for quantum annealing

Abstract

Quantum annealing is an optimization technique which potentially leverages quantum tunneling to enhance computational performance. Existing quantum annealers use superconducting flux qubits with short coherence times, limited primarily by the use of large persistent currents $I_{\mathrm{p}}$. Here, we examine an alternative approach, using qubits with smaller $I_{\mathrm{p}}$ and longer coherence times. We demonstrate tunable coupling, a basic building block for quantum annealing, between two flux qubits with small ($\sim 50\mathrm{nA}$) persistent currents. Furthermore, we characterize qubit coherence as a function of coupler setting and investigate the effect of flux noise in the coupler loop on qubit coherence. Our results provide insight into the available design space for next-generation quantum annealers with improved coherence.

References in corpus (11)

• Dynamical decoupling and noise spectroscopy with a superconducting flux qubit
• Controllable coupling of superconducting flux qubits
• Suppressing relaxation in superconducting qubits by quasiparticle pumping
• Observation of classical-quantum crossover of 1/f flux noise and its paramagnetic temperature dependence
• Interqubit coupling mediated by a high-excitation-energy quantum object
• Geometrical dependence of low frequency noise in superconducting flux qubits
• Mediated tunable coupling of flux qubits
• Ground-state energy of the electron liquid in ultrathin wires
• Fast quantum limited read-out of a superconducting qubit using a slow oscillator
• Spectroscopy of three strongly coupled flux qubits
• Realization of a classical counterpart of a scalable design for adiabatic quantum computation

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