120 research outputs found
Macroscopic optomechanics from displaced single-photon entanglement
Displaced single-photon entanglement is a simple form of optical
entanglement, obtained by sending a photon on a beamsplitter and subsequently
applying a displacement operation. We show that it can generate, through a
momentum transfer in the pulsed regime, an optomechanical entangled state
involving macroscopically distinct mechanical components, even if the
optomechanical system operates in the single-photon weak coupling regime. We
discuss the experimental feasibility of this approach and show that it might
open up a way for testing unconventional decoherence models.Comment: 10 pages, 4 figures, submission coordinated with Gohbadi et al. who
reported on similar result
Time-Continuous Bell Measurements
We combine the concept of Bell measurements, in which two systems are
projected into a maximally entangled state, with the concept of continuous
measurements, which concerns the evolution of a continuously monitored quantum
system. For such time-continuous Bell measurements we derive the corresponding
stochastic Schr\"odinger equations, as well as the unconditional feedback
master equations. Our results apply to a wide range of physical systems, and
are easily adapted to describe an arbitrary number of systems and measurements.
Time-continuous Bell measurements therefore provide a versatile tool for the
control of complex quantum systems and networks. As examples we show show that
(i) two two-level systems can be deterministically entangled via homodyne
detection, tolerating photon loss up to 50%, and (ii) a quantum state of light
can be continuously teleported to a mechanical oscillator, which works under
the same conditions as are required for optomechanical ground state cooling.Comment: 4+4 pages, 4 figure
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