Carbon Nanotubes Flex as Qubits

Physics 14, s96
A suspended carbon nanotube coupled to a double quantum dot makes a mechanical oscillator that serves as a qubit.
F. Pistolesi/University of Bordeaux

Many of today’s quantum computers encode information in fragile quantum states that are difficult to maintain and scale up. A qubit that instead switches between two mechanical states could bring to quantum computing and sensing the high quality and practical manipulability of mechanical oscillators. Fabio Pistolesi, at the French National Center for Scientific Research (CNRS) and the University of Bordeaux, and his colleagues now propose to implement such a qubit in the form of a carbon nanotube whose flexing behavior is determined by the electronic states of two quantum dots [1]. The design could be used to develop quantum devices with large numbers of qubits and long qubit decoherence times.

A mechanical oscillator can be made into a qubit by introducing a controlled deviation from simple harmonic oscillation. This deviation ensures that a driving force can excite only specific energy levels, corresponding to the qubit’s two states. In the device proposed by Pistolesi and his colleagues, this deviation would be achieved by coupling the flexural modes of a suspended carbon nanotube to two quantum dots—“artificial atoms” with discrete electronic states—formed in the nanotube itself. The researchers show theoretically that the qubit could be prepared in a given state (one of the nanotube’s two lowest oscillation amplitudes) by manipulating the quantum dots’ electron localization. The two states could be easily read by a microwave signal. The researchers also show how a logic gate could be implemented to entangle two qubits.

Their robust quantum states make the mechanical oscillators a promising quantum-computing platform. But, the researchers say, because of their sensitivity to classical forces, the oscillators also have potential for detecting faint changes in acceleration, gravity, magnetic moments, and electric forces.

–Rachel Berkowitz

Rachel Berkowitz is a Corresponding Editor for Physics based in Vancouver, Canada.


  1. F. Pistolesi et al., “Proposal for a nanomechanical qubit,” Phys. Rev. X 11, 031027 (2021).

Subject Areas

Quantum Physics

Related Articles

Turning a Quantum Computer into a Time Crystal
Quantum Information

Turning a Quantum Computer into a Time Crystal

Google’s Sycamore quantum processor can simulate an elusive quantum system called a discrete time crystal. Read More »

Superpositions of Chiral Molecules
Chemical Physics

Superpositions of Chiral Molecules

Matter-wave diffraction can put chiral molecules into superpositions of left- and right-handed forms, enabling new studies of how the two states interact with their environment. Read More »

Controlling the Phase Transition in Superfluid Helium-3

Controlling the Phase Transition in Superfluid Helium-3

Researchers demonstrate that they can suppress the formation of defects that appear in superfluid helium-3 when it undergoes a continuous phase transition, allowing them to influence the form of the system’s final phase. Read More »

More Articles