Seminar "Coherence-Correlations-Complexity", Dept. of Theoretical Physics, Wrocław University of Technology

13:15, 15-12-09
Sala 320a bud. A-1, Politechnika Wrocławska

Dynamics of entanglement of two singlet-triplet qubits: role of nuclear spin baths and charge noise

Igor Bragar

Instytut Fizyki Polskiej Akademii Nauk w Warszawie

A singlet-triplet (S-T) qubits is a promising realization of a spin qubit, in which a quantum state of the qubit is stored in the joint spin state of two electrons located in two quantum dots [1]. The two states of the logical qubit are the singlet |Si and spin-unpolarized triplet |T0> two-electron states. Recently it has been shown that it is possible in the experiment to perform a procedure of entangling of two S-T qubits [2]. However, the states obtained in that experiment were not maximally entangled – due to interaction with environmental noise these states were partially mixed. In the talk I will present a theoretical analysis of factors that do not allow for obtaining a maximally entangled state of two S-T qubits: fluctuations of gradient of effective magnetic field (the Overhauser field due to the nuclei) between the two dots electrons in a qubit, and fluctuations of the exchange splitting between |S> and |T0> states, caused by 1/f-like charge noise. This research is supported by funds of Polish National Science Center (NCN), grant no. DEC-2012/07/B/ST3/03616.

[1] J. R. Petta et al., Science 309, 2180 (2005).
[2] M. D. Shulman et al., Science 336, 202 (2012).

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