Abstract
We construct quantum error-correcting codes that embed a finite-dimensional code space in the infinite-dimensional Hilbert space of rotational states of a rigid body. These codes, which protect against both drift in the body’s orientation and small changes in its angular momentum, may be well suited for robust storage and coherent processing of quantum information using rotational states of a polyatomic molecule. Extensions of such codes to rigid bodies with a symmetry axis are compatible with rotational states of diatomic molecules as well as nuclear states of molecules and atoms. We also describe codes associated with general non-Abelian groups and develop orthogonality relations for coset spaces, laying the groundwork for quantum information processing with exotic configuration spaces.
- Received 18 November 2019
- Revised 27 May 2020
- Accepted 21 July 2020
DOI:https://doi.org/10.1103/PhysRevX.10.031050
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
synopsis
Protecting Molecular Qubits from Noise
Published 1 September 2020
A new proposal for how to encode quantum information in the rotational states of individual molecules could protect these qubits from losing information as a result of noise.
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Popular Summary
Quantum computers may someday be able to solve hard problems that are beyond the reach of existing or foreseeable classical digital technology. The information processing unit of a quantum computer is called a qubit, and today’s most powerful quantum computers are of modest size, containing only about 50 qubits. Furthermore, the qubits are hard to control, so that the computer often makes errors. Scaling up to much larger, more powerful quantum computers poses enormous scientific and engineering challenges. Here, we propose a step toward that goal with a novel qubit design based on a rotating molecule.
A qubit can be realized physically in many ways, such as the internal state of an atom, the spin of a single electron, or the excitation level of a quantized electrical circuit. All of these approaches to building quantum hardware are steadily advancing, but it is still far from clear which, if any, of the existing platforms can be scaled up to large devices capable of solving hard problems. Therefore, it is important to investigate alternatives. One recently emerging idea is that a qubit could be carried by the quantized rotational motion of a polyatomic molecule. Our proposed novel encoding of a qubit in a rotating molecule could have a substantial advantage over previous proposals, because the encoded qubit is intrinsically robust against laboratory noise and therefore less susceptible to error.
Our qubit realization is ambitious from the perspective of present-day technology for manipulating individual molecules, but not unreasonably so. We propose it as a challenging but reachable goal for the molecular physics community.