1,572 research outputs found
Generation of Total Angular Momentum Eigenstates in Remote Qubits
We propose a scheme enabling the universal coupling of angular momentum of
remote noninteracting qubits using linear optical tools only. Our system
consists of single-photon emitters in a -configuration that are
entangled among their long-lived ground-state qubits through suitably designed
measurements of the emitted photons. In this manner, we present an
experimentally feasible algorithm that is able to generate any of the
symmetric and nonsymmetric total angular momentum eigenstates spanning the
Hilbert space of the -qubit compound.Comment: 5 pages, 4 figures, improved presentation. Accepted in Physical
Review
A versatile source of polarization-entangled photons
We propose a method for the generation of a large variety of entangled
states, encoded in the polarization degrees of freedom of N photons, within the
same experimental setup. Starting with uncorrelated photons, emitted from N
arbitrary single photon sources, and using linear optical tools only, we
demonstrate the creation of all symmetric states, e.g., GHZ- and W-states, as
well as all symmetric and non-symmetric total angular momentum eigenstates of
the N qubit compound.Comment: 4 pages, 3 figure
Impact of ultrafast electronic damage in single particle x-ray imaging experiments
In single particle coherent x-ray diffraction imaging experiments, performed
at x-ray free-electron lasers (XFELs), samples are exposed to intense x-ray
pulses to obtain single-shot diffraction patterns. The high intensity induces
electronic dynamics on the femtosecond time scale in the system, which can
reduce the contrast of the obtained diffraction patterns and adds an isotropic
background. We quantify the degradation of the diffraction pattern from
ultrafast electronic damage by performing simulations on a biological sample
exposed to x-ray pulses with different parameters. We find that the contrast is
substantially reduced and the background is considerably strong only if almost
all electrons are removed from their parent atoms. This happens at fluences of
at least one order of magnitude larger than provided at currently available
XFEL sources.Comment: 15 pages, 3 figures submitted to PR
Single-photon excitation of a coherent state: catching the elementary step of stimulated light emission
When a single quantum of electromagnetic field excitation is added to the
same spatio-temporal mode of a coherent state, a new field state is generated
that exhibits intermediate properties between those of the two parents. Such a
single-photon-added coherent state is obtained by the action of the photon
creation operator on a coherent state and can thus be regarded as the result of
the most elementary excitation process of a classical light field. Here we
present and describe in depth the experimental realization of such states and
their complete analysis by means of a novel ultrafast, time-domain, quantum
homodyne tomography technique clearly revealing their non-classical character.Comment: 9 pages, 9 figures. Accepted for publication in Phys. Rev.
Influence of phonons on exciton-photon interaction and photon statistics of a quantum dot
In this paper, we investigate, phonon effects on the optical properties of a
spherical quantum dot. For this purpose, we consider the interaction of a
spherical quantum dot with classical and quantum fields while the exciton of
quantum dot interacts with a solid state reservoir. We show that phonons
strongly affect the Rabi oscillations and optical coherence on first
picoseconds of dynamics. We consider the quantum statistics of emitted photons
by quantum dot and we show that these photons are anti-bunched and obey the
sub-Poissonian statistics. In addition, we examine the effects of detuning and
interaction of quantum dot with the cavity mode on optical coherence of energy
levels. The effects of detuning and interaction of quantum dot with cavity mode
on optical coherence of energy levels are compared to the effects of its
interaction with classical pulse
Constrained MaxLik reconstruction of multimode photon distributions
We address the reconstruction of the full photon distribution of multimode
fields generated by seeded parametric down-conversion (PDC). Our scheme is
based on on/off avalanche photodetection assisted by maximum-likelihood
(MaxLik) estimation and does not involve photon counting. We present a novel
constrained MaxLik method that incorporates the request of finite energy to
improve the rate of convergence and, in turn, the overall accuracy of the
reconstruction
Driven harmonic oscillator as a quantum simulator for open systems
We show theoretically how a driven harmonic oscillator can be used as a
quantum simulator for non-Markovian damped harmonic oscillator. In the general
framework, the results demonstrate the possibility to use a closed system as a
simulator for open quantum systems. The quantum simulator is based on sets of
controlled drives of the closed harmonic oscillator with appropriately tailored
electric field pulses. The non-Markovian dynamics of the damped harmonic
oscillator is obtained by using the information about the spectral density of
the open system when averaging over the drives of the closed oscillator. We
consider single trapped ions as a specific physical implementation of the
simulator, and we show how the simulator approach reveals new physical insight
into the open system dynamics, e.g. the characteristic quantum mechanical
non-Markovian oscillatory behavior of the energy of the damped oscillator,
usually obtained by the non-Lindblad-type master equation, can have a simple
semiclassical interpretation.Comment: 10 pages, 4 figures. V2: Minor modifications and added 2 appendixes
for more details about calculation
Operational Theory of Homodyne Detection
We discuss a balanced homodyne detection scheme with imperfect detectors in
the framework of the operational approach to quantum measurement. We show that
a realistic homodyne measurement is described by a family of operational
observables that depends on the experimental setup, rather than a single field
quadrature operator. We find an explicit form of this family, which fully
characterizes the experimental device and is independent of a specific state of
the measured system. We also derive operational homodyne observables for the
setup with a random phase, which has been recently applied in an ultrafast
measurement of the photon statistics of a pulsed diode laser. The operational
formulation directly gives the relation between the detected noise and the
intrinsic quantum fluctuations of the measured field. We demonstrate this on
two examples: the operational uncertainty relation for the field quadratures,
and the homodyne detection of suppressed fluctuations in photon statistics.Comment: 7 pages, REVTe
Phase-dependent which-way information
We introduce a new observable for reading out a which-way detector in a
Young-type interferometer whose eigenstates either contain full which-way
information or none at all. We calculate the which-way knowledge K that can be
retrieved from this observable and find that K depends on the phase difference
\delta that the interfering object accumulates on its way from either slit to
the detector. In particular, it turns out that K(\delta) has an upper bound of
1, almost independent of the visibility V of the interference pattern generated
by the interfering object on a screen, which is in marked contrast to the
well-known inequality K^2 + V^2 <= 1 (cf. B.-G. Englert, Phys. Rev. Lett. 77,
2154 (1996)).Comment: 7 pages, 4 figure
Cavity quantum electro-optics
The quantum dynamics of the coupling between a cavity optical field and a
resonator microwave field via the electro-optic effect is studied. This
coupling has the same form as the opto-mechanical coupling via radiation
pressure, so all previously considered opto-mechanical effects can in principle
be observed in electro-optic systems as well. In particular, I point out the
possibilities of laser cooling of the microwave mode, entanglement between the
optical mode and the microwave mode via electro-optic parametric amplification,
and back-action-evading optical measurements of a microwave quadrature.Comment: 6 pages, 3 figures; v2: updated and submitted, v3: extended, accepted
by Physical Review
- …