Double joint seminar Department of Mathematics – CNR BEC

28 March 2018
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Luogo: Dipartimento di Matematica, via Sommarive, 14 - Povo (TN) - Aula Seminari "-1"
Ore: 11:30 - 12:20 e 12:40 - 13:30

Il seminario si dividerà in due interventi di 50 minuti l'uno intervallati da una pausa di 20 minuti per le domande.


  • Luca Dellantonio (Niels Bohr Institute, University of Copenhagen, Danmark)

Quantum nondemolition measurement of mechanical motion quanta


The fields of opto- and electromechanics have facilitated numerous advances in the areas of precision measurement and sensing, ultimately driving the studies of mechanical systems into the quantum regime. To date, however, the quantization of the mechanical motion and the associated quantum jumps between phonon states remains elusive. For optomechanical systems, the coupling to the environment was shown to preclude the detection of the mechanical mode occupation, unless strong single photon optomechanical coupling is achieved. Here, we propose and analyse an electromechanical setup, which allows us to overcome this limitation and resolve the energy levels of a mechanical oscillator. We find that the heating of the membrane, caused by the interaction with the environment and unwanted couplings, can be suppressed for carefully designed electromechanical systems. The results suggest that phonon number measurement is within reach for modern electromechanical setups.

High dimensional mdi-QKD on 2D subspaces


Measurement device independent quantum key distribution (mdi-QKD), resolves the detection side channel attacks. However, compared to point-to-point QKD protocols, mdi-QKD is limited in terms of secret key generation, due to post-selection Bell measurements. We use high dimensional encoding (qudits) to improve the performance of current mdi-QKD implementations. Our analysis includes phase errors, imperfect sources and dark counts to mimic real systems. The secret key rate is derived in the single photon case, while the security is extended to weak coherent pulses with decoy states.
Compared to the bidimensional case, we show an improvement in terms of key generation, mostly in the detector saturation regime. Our work determines, for different experimental conditions, the optimal setup for high dimensional mdi-QKD (HD-mdi-QKD).

Referenti: Alessandra Bernardi e Davide Pastorello (Dipartimento di Matematica), Iacopo Carusotto (CNR BEC)