Mechanical oscillators have been demonstrated with very high quality factors over a wide range of frequencies. They also couple to a wide variety of fields and forces, making them ideal as sensors. The realization of a mechanically based quantum bit could therefore provide an important new platform for quantum computation and sensing. Here, we show that by coupling one of the flexural modes of a suspended carbon nanotube to the charge states of a double quantum dot defined in the nanotube, it is possible to induce sufficient anharmonicity in the mechanical oscillator so that the coupled system can be used as a mechanical quantum bit. However, these results can only be achieved when the device enters the ultrastrong coupling regime. We discuss the conditions for the anharmonicity to appear, and we show that the Hamiltonian can be mapped onto an anharmonic oscillator, allowing us to work out the energy level structure and find how decoherence from the quantum dot and the mechanical oscillator is inherited by the qubit. Remarkably, the dephasing due to the quantum dot is expected to be reduced by several orders of magnitude in the coupled system. We outline qubit control, readout protocols, the realization of a CNOT gate by coupling two qubits to a microwave cavity, and finally how the qubit can be used as a static-force quantum sensor.

中文翻译：

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纳米力学量子位提案

机械振荡器已被证明在很宽的频率范围内具有非常高的品质因数。它们还与各种场和力耦合，使它们成为理想的传感器。因此，基于机械的量子位的实现可以为量子计算和传感提供一个重要的新平台。在这里，我们表明，通过将悬浮碳纳米管的弯曲模式之一与纳米管中定义的双量子点的电荷态耦合，可以在机械振荡器中引起足够的非谐性，从而可以使用耦合系统作为机械量子位。然而，只有当器件进入超强耦合状态时才能实现这些结果。我们讨论非谐出现的条件，我们展示了哈密顿量可以映射到非谐振荡器上，这使我们能够计算出能级结构，并找出量子位如何继承来自量子点和机械振荡器的退相干。值得注意的是，在耦合系统中，由于量子点引起的移相预计将减少几个数量级。我们概述了量子位控制、读出协议、通过将两个量子位耦合到微波腔来实现 CNOT 门，以及最后如何将量子位用作静力量子传感器。