Description
Encodes a logical Hilbert space, finite- or infinite-dimensional, into a physical Hilbert space of \(L^2\)-normalizable functions on either the integers \(\mathbb Z\) or the circle group \(U(1)\). Ideal codewords may not be normalizable because the space is infinite-dimensional, so approximate versions have to be constructed in practice.Protection
Rotor generalized Pauli error basis
A rotor analogue of the Pauli string basis for qubit codes consists of rotor generalized Pauli operators.
Rotor generalized Pauli strings: For a single rotor, its elements are products of exponentials of the rotor's angular position (\(\hat\phi\)) and angular momentum (\(\hat L\)) operators, acting on the rotor's angular position states \(|\phi\rangle\) for \(\phi\in U(1)\) as \begin{align} e^{-i\varphi\hat{L}}\left|\phi\right\rangle =\left|\phi+\varphi\right\rangle \,\,\text{ and }\,\,e^{i\ell\hat{\phi}}\left|\phi\right\rangle =e^{i\ell\phi}\left|\phi\right\rangle ~, \tag*{(1)}\end{align} where \(\varphi\in U(1)\) and \(\ell\in\mathbb{Z}\). For multiple rotors, error set elements are tensor products of elements of the single-rotor error set, characterized by vectors of angle and integer coefficients multiplying vectors of angular momentum \(\hat{\boldsymbol{L}}\) and angular position \(\hat{\boldsymbol{\phi}}\) operators.
Gates
The normalizer of the rotor Pauli group is the \(n\)-rotor Clifford group [1,2]. The rotor Clifford group permutes rotor Pauli operators amongst themselves, and, up to any phases, is equivalent to \(U(1)^{n(n+1)/2} \rtimes GL(n,\mathbb{Z})\) [3].Notes
See Refs. [4][2; Sec. IV] for introductions to rotor Hilbert spaces.Cousin
- Square-lattice GKP code— Because square-lattice GKP error states are parameterized by two modular (i.e., periodic) variables of position and momentum, measuring one of the GKP stabilizers constrains the oscillator Hilbert space into that of a rotor.
Member of code lists
Primary Hierarchy
References
- [1]
- J. Bermejo-Vega, C. Y.-Y. Lin, and M. V. den Nest, “Normalizer circuits and a Gottesman-Knill theorem for infinite-dimensional systems”, (2015) arXiv:1409.3208
- [2]
- V. V. Albert, J. P. Covey, and J. Preskill, “Robust Encoding of a Qubit in a Molecule”, Physical Review X 10, (2020) arXiv:1911.00099 DOI
- [3]
- Y. Xu, Y. Wang, and V. V. Albert, “Multimode rotation-symmetric bosonic codes from homological rotor codes”, Physical Review A 110, (2024) arXiv:2311.07679 DOI
- [4]
- V. V. Albert, S. Pascazio, and M. H. Devoret, “General phase spaces: from discrete variables to rotor and continuum limits”, Journal of Physics A: Mathematical and Theoretical 50, 504002 (2017) arXiv:1709.04460 DOI
Page edit log
- Austin He (2024-04-19) — most recent
- Victor V. Albert (2022-07-27)
Cite as:
“Rotor code”, The Error Correction Zoo (V. V. Albert & P. Faist, eds.), 2024. https://errorcorrectionzoo.org/c/rotor
Github: https://github.com/errorcorrectionzoo/eczoo_data/edit/main/codes/quantum/groups/rotors/rotor.yml.