2006/09/30 by Geza Toth, G. Tóth, Juan José García‐Ripoll +1 · 2 citations
Computer Science · Mathematics · Physics and Astronomy · #Algorithm #Block (permutation group theory) #Combinatorics #Computation #Computer science #Imperfect #Mathematics #Matrix (chemical analysis) #Quantum #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum algorithm #Quantum and electron transport phenomena #Quantum computer #Quantum error correction #Quantum mechanics #Quantum phase estimation algorithm #Random matrix #Set (abstract data type) #Simple (philosophy) #Unitary state #quant-ph
paper · pdf · doi:10.1103/physreva.75.042311
published as Phys. Rev. A 75, 042311 (2007) · 11 pages including 6 figures, revtex4; v2: presentation improved, sections VI and VII added; v3: small changes before publication
openalex publication_date 2007/04/11 · arxiv created 2007/04/26 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present an efficient algorithm for twirling a multiqudit quantum state. The algorithm can be used for approximating the twirling operation in an ensemble of physical systems in which the systems cannot be individually accessed. It can also be used for computing the twirled density matrix on a classical computer. The method is based on a simple nonunitary operation involving a random unitary. When applying this basic building block iteratively, the mean squared error of the approximation decays exponentially. In contrast, when averaging over random unitary matrices the error decreases only algebraically. We present evidence that the unitaries in our algorithm can come from a very imperfect random source or can even be chosen deterministically from a set of cyclically alternating matrices. Based on these ideas we present a quantum circuit realizing twirling efficiently.