21 research outputs found
An experimental demonstration of single photon nonlocality
In this letter we experimentally implement a single photon Bell test based on
the ideas of S. Tan et al. [Phys. Rev. Lett., vol. 66, 252 (1991)] and L. Hardy
[Phys. Rev. Lett.,vol. 73, 2279 (1994)]. A double heterodyne measurement is
used to measure correlations in the Fock space spanned by zero and one photons.
Local oscillators used in the correlation measurement are distributed to two
observers by co-propagating it in an orthogonal polarization mode. This method
eliminates the need for interferometrical stability in the setup, consequently
making it a robust and scalable method.Comment: 4 pages, 3 figures, revtex4 forma
Non-adiabatic holonomic quantum computation
We develop a non-adiabatic generalization of holonomic quantum computation in
which high-speed universal quantum gates can be realized by using non-Abelian
geometric phases. We show how a set of non-adiabatic holonomic one- and
two-qubit gates can be implemented by utilizing optical transitions in a
generic three-level configuration. Our scheme opens up for universal
holonomic quantum computation on qubits characterized by short coherence times.Comment: Some changes, journal reference adde
Detecting magnetically guided atoms with an optical cavity
We show that a low finesse cavity can be efficient for detecting neutral
atoms. The low finesse can be compensated for by decreasing the mode waist of
the cavity. We have used a near concentric resonator with a beam waist of
12m and a finesse of only 1100 to detect magnetically guided Rb atoms with
a detection sensitivity of 0.1 atom in the mode volume. For future experiments
on single atom detection and cavity QED applications, it should be very
beneficial to use miniaturized optical resonator integrated on atom chips.Comment: To appear in Optics Letter
A simple integrated single-atom detector
We present a reliable and robust integrated fluorescence detector capable of
detecting single atoms. The detector consists of a tapered lensed single-mode
fiber for precise delivery of excitation light and a multimode fiber to collect
the fluorescence. Both are mounted in lithographically defined SU-8 holding
structures on an atom chip. Rb87 atoms propagating freely in a magnetic guide
are detected with an efficiency of up to 66%, and a signal-to-noise ratio in
excess of 100 is obtained for short integration times.Comment: 3 pages, 3 figure
Quantum limits on phase-shift detection using multimode interferometers
Fundamental phase-shift detection properties of optical multimode
interferometers are analyzed. Limits on perfectly distinguishable phase shifts
are derived for general quantum states of a given average energy. In contrast
to earlier work, the limits are found to be independent of the number of
interfering modes. However, the reported bounds are consistent with the
Heisenberg limit. A short discussion on the concept of well-defined relative
phase is also included.Comment: 6 pages, 3 figures, REVTeX, uses epsf.st
Multi Mode Interferometer for Guided Matter Waves
We describe the fundamental features of an interferometer for guided matter
waves based on Y-beam splitters and show that, in a quasi two-dimensional
regime, such a device exhibits high contrast fringes even in a multi mode
regime and fed from a thermal source.Comment: Final version (accepted to PRL
Atom Chips
Atoms can be trapped and guided using nano-fabricated wires on surfaces,
achieving the scales required by quantum information proposals. These Atom
Chips form the basis for robust and widespread applications of cold atoms
ranging from atom optics to fundamental questions in mesoscopic physics, and
possibly quantum information systems