Decoherence: obstacle and helping friend

Interaction of a coherently controlled two-level quantum system (qubit) with its environment leads to decoherence of its quantum states. That process kills quantum computing. However, instead of fighting it one can try to make use of extraordinary vulnerability of quantum coherence to external interferences. I will try to present theoretical basis for noise spectroscopy (reconstruction of noise spectral density in the environment) by means of decoherence measurement [1] and to explain how to characterize spectrum of cross-correlations between fluctuations in environments of two qubits [2]. I will also mention applications to dynamics of spin of electron interacting with environment composed of some nuclear spins [3].

[1]       P.Szańkowski, G.Ramon, J.Krzywda, D.Kwiatkowski, and Ł.Cywiński, a Topical Review to appear J.Phys.:Condens. Matt., arXiv:1705.02262.
[2]       P.Szańkowski, M.Trippenbach, and Ł.Cywiński, Phys. Rev. A 94, 012109 (2016), arXiv:1507.03897.
[3]       F.K.Malinowski et al, Nature Nanotechnology  12, 16 (2017), arXiv:1601.06677; Phys. Rev. Lett. 118, 177702 (2017), arXiv:1701.01855

All interested persons are invited
M. Kowal, W. Piechocki, L. Roszkowski, J. Skalski, L. Szymanowski