8 research outputs found
Quantum nondemolition detection of a propagating microwave photon
The ability to nondestructively detect the presence of a single, traveling
photon has been a long-standing goal in optics, with applications in quantum
information and measurement. Realising such a detector is complicated by the
fact that photon-photon interactions are typically very weak. At microwave
frequencies, very strong effective photon-photon interactions in a waveguide
have recently been demonstrated. Here we show how this type of interaction can
be used to realize a quantum nondemolition measurement of a single propagating
microwave photon. The scheme we propose uses a chain of solid-state 3-level
systems (transmons), cascaded through circulators which suppress photon
backscattering. Our theoretical analysis shows that microwave-photon detection
with fidelity around 90% can be realized with existing technologies
Quantum trajectories for propagating Fock states
We derive quantum trajectories (also known as stochastic master equations)
that describe an arbitrary quantum system probed by a propagating wave packet
of light prepared in a continuous-mode Fock state. We consider three detection
schemes of the output light: photon counting, homodyne detection, and
heterodyne detection. We generalize to input field states that are
superpositions and or mixtures of Fock states and illustrate the formalism with
several examples.Comment: 20 pages, 4 figure
Quantum master equation and filter for systems driven by fields in a single photon state
The aim of this paper is to determine quantum master and filter equations for
systems coupled to continuous-mode single photon fields. The system and field
are described using a quantum stochastic unitary model, where the
continuous-mode single photon state for the field is determined by a wavepacket
pulse shape. The master equation is derived from this model and is given in
terms of a system of coupled equations. The output field carries information
about the system from the scattered photon, and is continuously monitored. The
quantum filter is determined with the aid of an embedding of the system into a
larger system, and is given by a system of coupled stochastic differential
equations. An example is provided to illustrate the main results.Comment: 7 pages, 2 figures. Accepted for publication in the joint 50th IEEE
Conference on Decision and Control (CDC) and European Control Conference
(ECC), 2011 (http://control.disp.uniroma2.it/cdcecc2011/