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Pauli Group


For n>=1, the n-qubit Pauli group is the finite matrix group of 2^n×2^n matrices consisting of scalar phases times Kronecker products of the Pauli matrices. More explicitly, on writing sigma_0=I, it is

 P_n={i^ksigma_(j_1) tensor ... tensor sigma_(j_n)|(k,j_1,...,j_n) in {0,1,2,3}^(n+1)}.

Here, I is the 2×2 identity matrix and i is the imaginary unit. This convention includes all four scalar phases. Hashagen et al. (2018) call the subgroup generated by Kronecker products of sigma_1 and sigma_3 the real Pauli group, while Harper et al. (2021) call P_n/<iI> the Paulis modulo phase. These groups have different orders, so the convention must be stated when quoting an order.

The group P_n has group order 4^(n+1). Its group center is Z(P_n)={I,-I,iI,-iI}=C_4, and the quotient group by the center is P_n/Z(P_n)=C_2^(2n). The Pauli group is fundamental to the stabilizer formalism for quantum error-correcting codes (Gottesman 1997, Nielsen and Chuang 2000).

The one-qubit Pauli group P_1, also denoted P_1 (and P(1) by Knill 2026), has group order 16. It is isomorphic to the central product of the dihedral group D_4 and the cyclic group C_4, and contains a subgroup isomorphic to the quaternion group Q_8. The Cayley graph of P_1 generated by the three Pauli matrices is the Möbius-Kantor graph (Bavuma et al. 2024).


See also

Cayley Graph, Möbius-Kantor Graph, Pauli Matrices, Quantum Error-Correcting Code, Quaternion Group, Qubit

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References

Bavuma, Y.; D'Angeli, D.; Donno, A.; and Russo, F. G. "On an Infinite Family of Integral Cayley Graphs of Pauli Groups." J. Algebra 659, 148-182, 2024. https://doi.org/10.1016/j.jalgebra.2024.06.017.Gottesman, D. "Stabilizer Codes and Quantum Error Correction." Ph.D. thesis. Pasadena, CA: California Institute of Technology, 28 May 1997. https://arxiv.org/abs/quant-ph/9705052.Harper, R.; Yu, W.; and Flammia, S. T. "Fast Estimation of Sparse Quantum Noise." PRX Quantum 2, 010322, 2021. https://doi.org/10.1103/PRXQuantum.2.010322.Hashagen, A. K.; Flammia, S. T.; Gross, D.; and Wallman, J. J. "Real Randomized Benchmarking." Quantum 2, 85, 2018. https://doi.org/10.22331/q-2018-08-22-85.Knill, O. "Remarks about the Möbius-Kantor Graph." 29 May 2026. https://arxiv.org/abs/2605.30799.Nielsen, M. and Chuang, I. Quantum Computation and Quantum Information. Cambridge, England: Cambridge University Press, 2000.

Cite this as:

Weisstein, Eric W. "Pauli Group." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/PauliGroup.html

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