Seminar of the ICMP

# Seminar of the ICMP

Quantum-limited detectors: the concept and many-body effects

Recently, a new experimentally-grounded tendency has appeared: to

consider certain types of quantum mesoscopic systems (such as quantum-point

contacts) as quantum-limited detector measuring quantum states of another

quantum systems (such as charge- and spin qubits). In the framework of such

ideology the physical interaction between these two subsystems of larger

quantum system plays two distinct roles: i) the influence of measured

subsystem on quantum detector (i.e. the output signal) and ii) the

decoherence of the measured subsystem which should be refered to as

detector's backaction on the former. Obviously, in the case of

superposition of measured system's quantum states, the acquisiton of

information about any of these states (by means of quantum detector signal)

cannot be faster than the measured system's superposition state

decoherence. The ratio of corresponded two rates (acquisition information

rate and decoherence rate) - defines the quantum detector's efficiency. In

my talk I'll highlight some principles behind the theory of quantum-limited

detectors and report on some interesting many-body interaction effects

which will be crucial for the quality of a broad class of prospective

quantum-limited detectors.

Couple of useful references:

[1] D. V. Averin and E. V. Sukhorukov, Phys. Rev. Lett. 95, 126803 (2005).

[2] G.Skorobagatko, A.Bruch, S.-V.Kusminskiy, A.Romito, "Interaction

effects on quantum-limited detectors",

arXiv:1609.07281 <https://arxiv.org/abs/1609.07281>