90 research outputs found
Beam Splitter for Spin Waves in Quantum Spin Network
We theoretically design and analytically study a controllable beam splitter
for the spin wave propagating in a star-shaped (e.g., a -shaped beam) spin
network. Such a solid state beam splitter can display quantum interference and
quantum entanglement by the well-aimed controls of interaction on nodes. It
will enable an elementary interferometric device for scalable quantum
information processing based on the solid system.Comment: 5 pages, 4 figures, derivation of formulae change
Comment on ``Manipulating the frequency entangled states by an acoutic-optical modulator''
A recent theoretical paper [1] proposes a scheme for entanglement swapping
utilizing acousto-optic modulators without requiring a Bell-state measurement.
In this comment, we show that the proposal is flawed and no entanglement
swapping can occur without measurement.Comment: 6 pages, 2 figures submitted to Phys. Rev
Spin correlated interferometry for polarized and unpolarized photons on a beam splitter
Spin interferometry of the 4th order for independent polarized as well as
unpolarized photons arriving simultaneously at a beam splitter and exhibiting
spin correlation while leaving it, is formulated and discussed in the quantum
approach. Beam splitter is recognized as a source of genuine singlet photon
states. Also, typical nonclassical beating between photons taking part in the
interference of the 4th order is given a polarization dependent explanation.Comment: RevTeX, 19 pages, 1 ps figure, author web page at
http://m3k.grad.hr/pavici
DadaGP: A Dataset of Tokenized GuitarPro Songs for Sequence Models
Originating in the Renaissance and burgeoning in the digital era, tablatures are a commonly used music notation system which provides explicit representations of instrument fingerings rather than pitches. GuitarPro has established itself as a widely used tablature format and software enabling musicians to edit and share songs for musical practice, learning, and composition. In this work, we present DadaGP, a new symbolic music dataset comprising 26,181 song scores in the GuitarPro format covering 739 musical genres, along with an accompanying tokenized format well-suited for generative sequence models such as the Transformer. The tokenized format is inspired by event-based MIDI encodings, often used in symbolic music generation models. The dataset is released with an encoder/decoder which converts GuitarPro files to tokens and back. We present results of a use case in which DadaGP is used to train a Transformer-based model to generate new songs in GuitarPro format. We discuss other relevant use cases for the dataset (guitar-bass transcription, music style transfer and artist/genre classification) as well as ethical implications. DadaGP opens up the possibility to train GuitarPro score generators, fine-tune models on custom data, create new styles of music, AI-powered songwriting apps, and human-AI improvisation
Violation of Bell's Inequality with Photons from Independent Sources
We report a violation of Bell's inequality using one photon from a parametric
down-conversion source and a second photon from an attenuated laser beam. The
two photons were entangled at a beam splitter using the post-selection
technique of Shih and Alley [Phys. Rev. Lett. 61, 2921 (1988)]. A quantum
interference pattern with a visibility of 91% was obtained using the photons
from these independent sources, as compared with a visibility of 99.4% using
two photons from a central parametric down-conversion source.Comment: 4 pages, 5 figures; minor change
Demonstration of Controllable Temporal Distinguishability in a Three-Photon State
Multi-photon interference is at the heart of the recently proposed linear
optical quantum computing scheme and plays an essential role in many protocols
in quantum information. Indistinguishability is what leads to the effect of
quantum interference. Optical interferometers such as Michaelson interferometer
provide a measure for second-order coherence at one-photon level and
Hong-Ou-Mandel interferometer was widely employed to describe two-photon
entanglement and indistinguishability. However, there is not an effective way
for a system of more than two photons. Recently, a new interferometric scheme
was proposed to quantify the degree of multi-photon distinguishability. Here we
report an experiment to implement the scheme for three-photon case. We are able
to generate three photons with different degrees of temporal distinguishability
and demonstrate how to characterize them by the visibility of three-photon
interference. This method of quantitative description of multi-photon
indistinguishability will have practical implications in the implementation of
quantum information protocols
Quantum interference with photon pairs created in spatially separated sources
We report on a quantum interference experiment to probe the coherence between
two photons coming from non degenerate photon pairs at telecom wavelength
created in spatially separated sources. The two photons are mixed on a beam
splitter and we observe a reduction of up to 84% in the coincidence count rate
when the photons are made indistinguishable. This experiment constitutes an
important step towards the realization of quantum teleportation and
entanglement swapping with independent sources.Comment: 5 pages, 2 figures, changes according to referee's comments,
discussions partly rewritte
Experimental Demonstration of Five-photon Entanglement and Open-destination Teleportation
Universal quantum error-correction requires the ability of manipulating
entanglement of five or more particles. Although entanglement of three or four
particles has been experimentally demonstrated and used to obtain the extreme
contradiction between quantum mechanics and local realism, the realization of
five-particle entanglement remains an experimental challenge. Meanwhile, a
crucial experimental challenge in multi-party quantum communication and
computation is the so-called open-destination teleportation. During
open-destination teleportation, an unknown quantum state of a single particle
is first teleported onto a N-particle coherent superposition to perform
distributed quantum information processing. At a later stage this teleported
state can be readout at any of the N particles for further applications by
performing a projection measurement on the remaining N-1 particles. Here, we
report a proof-of-principle demonstration of five-photon entanglement and
open-destination teleportation. In the experiment, we use two entangled photon
pairs to generate a four-photon entangled state, which is then combined with a
single photon state to achieve the experimental goals. The methods developed in
our experiment would have various applications e.g. in quantum secret sharing
and measurement-based quantum computation.Comment: 19 pages, 4 figures, submitted for publication on 15 October, 200
Delayed - Choice Entanglement - Swapping with Vacuum-One Photon Quantum States
We report the experimental realization of a recently discovered quantum
information protocol by Asher Peres implying an apparent non-local quantum
mechanical retrodiction effect. The demonstration is carried out by applying a
novel quantum optical method by which each singlet entangled state is
physically implemented by a two-dimensional subspace of Fock states of a mode
of the electromagnetic field, specifically the space spanned by the vacuum and
the one photon state, along lines suggested recently by E. Knill et al., Nature
409, 46 (2001) and by M. Duan et al., Nature 414, 413 (2001). The successful
implementation of the new technique is expected to play an important role in
modern quantum information and communication and in EPR quantum non-locality
studies
Probabilistic Quantum Logic Operations Using Polarizing Beam Splitters
It has previously been shown that probabilistic quantum logic operations can
be performed using linear optical elements, additional photons (ancilla), and
post-selection based on the output of single-photon detectors. Here we describe
the operation of several quantum logic operations of an elementary nature,
including a quantum parity check and a quantum encoder, and we show how they
can be combined to implement a controlled-NOT (CNOT) gate. All of these gates
can be constructed using polarizing beam splitters that completely transmit one
state of polarization and totally reflect the orthogonal state of polarization,
which allows a simple explanation of each operation. We also describe a
polarizing beam splitter implementation of a CNOT gate that is closely
analogous to the quantum teleportation technique previously suggested by
Gottesman and Chuang [Nature 402, p.390 (1999)]. Finally, our approach has the
interesting feature that it makes practical use of a quantum-eraser technique.Comment: 9 pages, RevTex; Submitted to Phys. Rev. A; additional references
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