Principal Investigators: Professor Paolo Tombesi / Professor Fulvio Esposito
The Project
Quantum Networks: Qudit and continuous variable networks
The main objective of this workpackage is to develop theory and experiment exploiting the rich structure of photons to build error-correction and error-avoidance schemes, and to implement few-qubit-scale algorithms in this direction.
Noise is an unwanted element of any communication and computation process, ever present in open systems because of the interaction with the surrounding environment. Several techniques used in classical communication can be implemented to protect quantum systems against noise. Some of them exploit a redundant encoding of the information to be conveyed over the channel (Quantum Error Correction); others have been designed to harness specific properties of the quantum states and channels (Decoherence-Free Subspaces), or to post-select pure quantum systems from an ensemble of imperfect ones (Purification, Distillation, Concentration protocols). All these techniques can be grouped under the name of “Passive Control” (PC). On the contrary, Active Control techniques (AC), aim to maintain the coherence of a quantum system by applying fast operations that decouple it from the environment. Although AC has been mainly developed in the field of Nuclear Magnetic Resonance, it can be realized in the contest of optical quantum communication as well.
The primary goal of work at the University of Camerino (UNICAM) is the experimental realization of a Bang-Bang Control, that is an active fast manipulation of photon polarization states devoted to the reduction of the decoherence effect from the environment. A basic theoretical model of the environment will be investigated and will be tested with numerical simulations. A cavity for the storage of photons will be realized and used as test-bed for an experimental proof of this principle. The cavity will be designed such that it is possible to insert a number of nonlinear birefringent optical elements in one arm, to simulate the decoherence in a controlled way, and in the other arm an opportune sequence of unitary operations, which represent the bang-bang control. A polarization entangled photon source will be constructed to directly test the setup at the single photon level, along with the necessary electronics for fast manipulation of the samples. In this respect UNICAM will also report on experimental progress towards the electronics for a two-way quantum communication protocol at telecom wavelengths. This protocol features a high tolerance of communication channel noise, thus matching the spirit of the research line described above.
Researchers within this workpackage will also study how optomechanical
systems can be profitably used for generating and manipulating
continuous-variable entanglement. Specifically, generation and detection of
entanglement between an electromagnetic field inside a Fabry-Perot cavity
and the mechanical mode of one cavity’s movable mirror will be investigated.
The entanglement should persist up to 20 K for oscillating mirrors with
nanogram masses. Finally, detection of weak mechanical forces with
optomechanical entanglement will also be investigated.
Other QAP Activities
Researchers at the University of Camerino are also involved with Pirelli
Research Laboratories on the use and characterization of new detectors for
quantum communication protocols, as well as for miniaturization of optical
devices.
List of Publications
QAP
A. Cere, M. Lucamarini, G. Di Giuseppe et al, Experimental Test of Two-Way Quantum Key Distribution in the Presence of Controlled Noise, Phys. Rev. Lett. 96 200501 (2006) quant-ph/0605118
M. Lucamarini, A. Cere, G. Di Giuseppe et al, Two-way Protocol for Quantum Cryptography with Imperfect Devices, accepted for publication in Open Systems and Information Dynamics quant-ph/0605106
S. Rebic, C. Ottaviani, G. Di Giuseppe et al, Assessment of a quantum phase gate operation based on nonlinear optics, Phys. Rev. A 74 032301 (2006) quant-ph/0605100
C. Genes, D. Vitali, P. Tombesi et al., Ground-state cooling of a micromechanical oscillator: comparing cold damping and cavity-assisted cooling schemes, submitted to Phys. Rev. Lett. quant-ph/07051728
D. Vitali, S. Mancini and P. Tombesi, Stationary entanglement between two movable mirrors in a classically driven Fabry-Perot cavity, accepted for publication in J. Phys. A quant-ph/0611038
G. Di Giuseppe, M. Lucamarini, A. Ceré, and P. Tombesi, Individual incoherent eavesdropping on a two-way quantum communication protocol, Proc. SPIE 6305 630502 (2006)