Magyar Tudományos Akadémia WIGNER FIZIKAI KUTATÓKÖZPONT|
SZILÁRDTESTFIZIKAI ÉS OPTIKAI INTÉZET
1121 Budapest, Konkoly-Thege út 29-33, tel. 392-2212
University of the Basque Country UPV/EHU, vendéglátó: Kiss Tamás
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
 G. Tóth and J.J. García-Ripoll, Efficient algorithm for multi-qudit twirling for ensemble quantum computation, Phys. Rev. A 75, 042311 (2007); quant-ph/0609052.
Minden érdeklődőt szívesen látunk!