6 research outputs found
Experimental inhibition of decoherence on flying qubits via bang-bang control
Decoherence may significantly affect the polarization state of optical pulses
propagating in dispersive media because of the unavoidable presence of more
than a single frequency in the envelope of the pulse. Here we report on the
suppression of polarization decoherence in a ring cavity obtained by properly
retooling for photonic qubits the ``bang-bang'' protection technique already
employed for nuclear spins and nuclear-quadrupole qubits. Our results show that
bang-bang control can be profitably extended to quantum information processes
involving flying polarization qubits.Comment: 5 pages, 3 figure
Measurement Induced Quantum Coherence Recovery
We show that measurement can recover the quantum coherence of a qubit in a
non-Markovian environment. The experimental demonstration in an optical system
is provided by comparing the visibilities (and fidelities) of the final states
with and without measurement. This method can be extended to other two-level
quantum systems and entangled states in a non-Markovian evolution environment.
It may also be used to implement other quantum information processing.Comment: 9 pages, 5 figure
Suppression of polarization decoherence for traveling light pulses via bang-bang dynamical decoupling
In the propagation of optical pulses through dispersive media, the frequency
degree of freedom acts as an effective decohering environment on the
polarization state of the pulse. Here we discuss the application of open-loop
dynamical-decoupling techniques for suppressing such a polarization decoherence
in one-way communication channels. We describe in detail the experimental proof
of principle of the "bang-bang" protection technique recently applied to flying
qubits in [Damodarakurup et al., Phys. Rev. Lett. 103, 040502]. Bang-bang
operations are implemented through appropriately oriented waveplates and
dynamical decoupling is shown to be potentially useful to contrast a generic
decoherence acting on polarization qubits propagating in dispersive media like,
e.g., optical fibers.Comment: 14 pages, 15 figure