276 research outputs found
Quantum interferometric optical lithography:towards arbitrary two-dimensional patterns
As demonstrated by Boto et al. [Phys. Rev. Lett. 85, 2733 (2000)], quantum
lithography offers an increase in resolution below the diffraction limit. Here,
we generalize this procedure in order to create patterns in one and two
dimensions. This renders quantum lithography a potentially useful tool in
nanotechnology.Comment: 9 pages, 5 figures Revte
Two-photon diffraction and quantum lithography
We report a proof-of-principle experimental demonstration of quantum
lithography. Utilizing the entangled nature of a two-photon state, the
experimental results have bettered the classical diffraction limit by a factor
of two. This is a quantum mechanical two-photon phenomenon but not a violation
of the uncertainty principle.Comment: 5 pages, 5 figures Submitted to Physical Review Letter
Coherent Superposition States as Quantum Rulers
We explore the sensitivity of an interferometer based on a quantum circuit
for coherent states. We show that its sensitivity is at the Heisenberg limit.
Moreover we show that this arrangement can measure very small length intervals
Entangled-State Lithography: Tailoring any Pattern with a Single State
We demonstrate a systematic approach to Heisenberg-limited lithographic image
formation using four-mode reciprocal binominal states. By controlling the
exposure pattern with a simple bank of birefringent plates, any pixel pattern
on a grid, occupying a square with the side half a
wavelength long, can be generated from a -photon state.Comment: 4 pages, 4 figure
Quantum enhanced positioning and clock synchronization
A wide variety of positioning and ranging procedures are based on repeatedly
sending electromagnetic pulses through space and measuring their time of
arrival. This paper shows that quantum entanglement and squeezing can be
employed to overcome the classical power/bandwidth limits on these procedures,
enhancing their accuracy. Frequency entangled pulses could be used to construct
quantum positioning systems (QPS), to perform clock synchronization, or to do
ranging (quantum radar): all of these techniques exhibit a similar enhancement
compared with analogous protocols that use classical light. Quantum
entanglement and squeezing have been exploited in the context of
interferometry, frequency measurements, lithography, and algorithms. Here, the
problem of positioning a party (say Alice) with respect to a fixed array of
reference points will be analyzed.Comment: 4 pages, 2 figures. Accepted for publication by Natur
Two-Photon Interferometry for High-Resolution Imaging
We discuss advantages of using non-classical states of light for two aspects
of optical imaging: creating of miniature images on photosensitive substrates,
which constitutes the foundation for optical lithography, and imaging of micro
objects. In both cases, the classical resolution limit given by the Rayleigh
criterion is approximately a half of the optical wavelength. It has been shown,
however, that by using multi-photon quantum states of the light field, and
multi-photon sensitive material or detector, this limit can be surpassed. We
give a rigorous quantum mechanical treatment of this problem, address some
particularly widespread misconceptions and discuss the requirements for turning
the research on quantum imaging into a practical technology.Comment: Presented at PQE 2001. To appear in Special Issue of Journal of
Modern Optic
Positioning and clock synchronization through entanglement
A method is proposed to employ entangled and squeezed light for determining
the position of a party and for synchronizing distant clocks. An accuracy gain
over analogous protocols that employ classical resources is demonstrated and a
quantum-cryptographic positioning application is given, which allows only
trusted parties to learn the position of whatever must be localized. The
presence of a lossy channel and imperfect photodetection is considered. The
advantages in using partially entangled states is discussed.Comment: Revised version. 9 pages, 6 figure
Imaging the human hippocampus with optically-pumped magnetoencephalography
Optically-pumped (OP) magnetometers allow magnetoencephalography (MEG) to be performed while a participantâs head is unconstrained. To fully leverage this new technology, and in particular its capacity for mobility, the
activity of deep brain structures which facilitate explorative behaviours such as navigation, must be detectable
using OP-MEG. One such crucial brain region is the hippocampus. Here we had three healthy adult participants
perform a hippocampal-dependent task â the imagination of novel scene imagery â while being scanned using OPMEG. A conjunction analysis across these three participants revealed a significant change in theta power in the
medial temporal lobe. The peak of this activated cluster was located in the anterior hippocampus. We repeated the
experiment with the same participants in a conventional SQUID-MEG scanner and found similar engagement of
the medial temporal lobe, also with a peak in the anterior hippocampus. These OP-MEG findings indicate exciting
new opportunities for investigating the neural correlates of a range of crucial cognitive functions in naturalistic
contexts including spatial navigation, episodic memory and social interactions
Full Quantum Analysis of Two-Photon Absorption Using Two-Photon Wavefunction: Comparison with One-Photon Absorption
For dissipation-free photon-photon interaction at the single photon level, we
analyze one-photon transition and two-photon transition induced by photon pairs
in three-level atoms using two-photon wavefunctions. We show that the
two-photon absorption can be substantially enhanced by adjusting the time
correlation of photon pairs. We study two typical cases: Gaussian wavefunction
and rectangular wavefunction. In the latter, we find that under special
conditions one-photon transition is completely suppressed while the high
probability of two-photon transition is maintained.Comment: 6 pages, 4 figure
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