46 research outputs found
Ghost imaging with engineered quantum states by Hong-Ou-Mandel interference
Traditional ghost imaging experiments exploit position correlations between
correlated states of light. These correlations occur directly in spontaneous
parametric down-conversion (SPDC), and in such a scenario, the two-photon state
used for ghost imaging is symmetric. Here we perform ghost imaging using an
anti-symmetric state, engineering the two-photon state symmetry by means of
Hong-Ou-Mandel interference. We use both symmetric and anti-symmetric states
and show that the ghost imaging setup configuration results in object-image
rotations depending on the state selected. Further, the object and imaging arms
employ spatial light modulators for the all-digital control of the projections,
being able to dynamically change the measuring technique and the spatial
properties of the states under study. Finally, we provide a detailed theory
that explains the reported observations.Comment: Published version. 19 pages, 5 figure
Optical sectioning in induced coherence tomography with frequency-entangled photons
We demonstrate a different scheme to perform optical sectioning of a sample
based on the concept of induced coherence [Zou et al., Phys. Rev. Lett. 67, 318
(1991)]. This can be viewed as a different type of optical coherence tomography
scheme where the varying reflectivity of the sample along the direction of
propagation of an optical beam translates into changes of the degree of
first-order coherence between two beams. As a practical advantage the scheme
allows probing the sample with one wavelength and measuring photons with
another wavelength. In a bio-imaging scenario, this would result in a deeper
penetration into the sample because of probing with longer wavelengths, while
still using the optimum wavelength for detection. The scheme proposed here
could achieve submicron axial resolution by making use of nonlinear parametric
sources with broad spectral bandwidth emission.Comment: Published version. 11 pages, 9 figure
Self-healing high-dimensional quantum key distribution using hybrid spin-orbit Bessel states
Using spatial modes for quantum key distribution (QKD) has become highly
topical due to their infinite dimensionality, promising high information
capacity per photon. However, spatial distortions reduce the feasible secret
key rates and compromise the security of a quantum channel. In an extreme form
such a distortion might be a physical obstacle, impeding line-of-sight for
free-space channels. Here, by controlling the radial degree of freedom of a
photon's spatial mode, we are able to demonstrate hybrid high-dimensional QKD
through obstacles with self-reconstructing single photons. We construct
high-dimensional mutually unbiased bases using spin-orbit hybrid states that
are radially modulated with a non-diffracting Bessel-Gaussian (BG) profile, and
show secure transmission through partially obstructed quantum links. Using a
prepare-measure protocol we report higher quantum state self-reconstruction and
information retention for the non-diffracting BG modes as compared to
Laguerre-Gaussian modes, obtaining a quantum bit error rate (QBER) that is up
to 3 times lower. This work highlights the importance of controlling the radial
mode of single photons in quantum information processing and communication as
well as the advantages of QKD with hybrid states.Comment: Published version, 15 pages, 6 figures, 2 table
Spatial mode detection by frequency upconversion
The efficient creation and detection of spatial modes of light has become
topical of late, driven by the need to increase photon-bit-rates in classical
and quantum communications. Such mode creation/detection is traditionally
achieved with tools based on linear optics. Here we put forward a new spatial
mode detection technique based on the nonlinear optical process of
sum-frequency generation. We outline the concept theoretically and demonstrate
it experimentally with intense laser beams carrying orbital angular momentum
and Hermite-Gaussian modes. Finally, we show that the method can be used to
transfer an image from the infrared band to the visible, which implies the
efficient conversion of many spatial modes.Comment: Published version, 4 pages, 5 figure
Complementarity relationship between first-order coherence and path distinguishability in an interferometer based on induced coherence
We consider an interferometer based on the concept of induced coherence,
where two signal photons that originate in different second-order nonlinear
crystals can interfere. We derive a complementarity relationship that links the
first-order coherence between the two interfering signal photons with a
parameter that quantifies the distinguishing information regarding the
nonlinear crystal where they originated. Astonishingly, the derived
relationship goes beyond the single-photon regime and is valid for any photon
flux rate generated. We show experimental results in the low photon-flux regime
that confirm the validity of the derived complementarity relationship.Comment: 6 pages, 6 figure
Enhancing the modal purity of orbital angular momentum photons
Orbital angular momentum (OAM) beams with topological charge ℓ are commonly generated and detected by modulating an incoming field with an azimuthal phase profile of the form exp(iℓϕ) by a variety of approaches. This results in unwanted radial modes and reduced power in the desired OAM mode. Here, we show how to enhance the modal purity in the creation and detection of classical OAM beams and in the quantum detection of OAM photons. Classically, we combine holographic and metasurface control to produce high purity OAM modes and show how to detect them with high efficiency, extending the demonstration to the quantum realm with spatial light modulators. We demonstrate ultra-high purity OAM modes in orders as high as ℓ = 100 and a doubling of dimensionality in the quantum OAM spectrum from a spontaneous parametric downconversion source. Our work offers a simple route to increase the channel capacity in classical and quantum communication using OAM modes as a basis