Quantum electromechanics: Quantum tunneling near resonance and qubits from buckling nanobars

TL;DR

This paper explores quantum tunneling phenomena in nanomechanical systems, drawing parallels with superconducting qubits, and proposes buckling nanobars as a new platform for quantum computing with detailed theoretical analysis and design suggestions.

Contribution

It introduces a mechanical qubit based on buckling nanobars, providing theoretical modeling, design proposals, and analysis of decoherence and detection methods.

Findings

Resonance peak splitting explained by quantum tunneling

Effective potential for buckling nanobars as two-level systems

Design strategies for nanomechanical qubits and their manipulation

Abstract

Analyzing recent experimental results, we find similar behaviors and a deep analogy between three-junction superconducting qubits and suspended carbon nanotubes. When these different systems are ac-driven near their resonances, the resonance single-peak, observed at weak driving, splits into two sub-peaks (Fig. 1) when the driving increases. This unusual behavior can be explained by considering quantum tunneling in a double well potential for both systems. Inspired by these experiments, we propose a mechanical qubit based on buckling nanobars--a NEMS so small as to be quantum coherent. To establish buckling nanobars as legitimate candidates for qubits, we calculate the effective buckling potential that produces the two-level system and identify the tunnel coupling between the two local states. We propose different designs of nanomechanical qubits and describe how they can be manipulated. Also, we outline possible decoherence channels and detection schemes. A comparison between nanobars and well studied superconducting qubits suggests several future experiments on quantum electromechanics.