456 research outputs found
Generation of orbital angular momentum bell states and their verification via accessible nonlinear witnesses
A "fair sampling" perspective on an apparent violation of duality
In the event in which a quantum mechanical particle can pass from an initial
state to a final state along two possible paths, the duality principle states
that "the simultaneous observation of wave and particle behavior is
prohibited". [M. O. Scully, B.-G. Englert, and H. Walther. Nature, 351:111-116,
1991.] emphasized the importance of additional degrees of freedom in the
context of complementarity. In this paper, we show how the consequences of
duality change when allowing for biased sampling, that is, postselected
measurements on specific degrees of freedom of the environment of the two-path
state. Our work contributes to the explanation of previous experimental
apparent violations of duality [R. Menzel, D. Puhlmann, A. Heuer, and W. P.
Schleich. Proc. Natl. Acad. Sci., 109(24):9314-9319, 2012.] and opens up the
way for novel experimental tests of duality.Comment: 10 pages, 8 figure
Direct Measurement of a 27-Dimensional Orbital-Angular-Momentum State Vector
The measurement of a quantum state poses a unique challenge for
experimentalists. Recently, the technique of "direct measurement" was proposed
for characterizing a quantum state in-situ through sequential weak and strong
measurements. While this method has been used for measuring polarization
states, its real potential lies in the measurement of states with a large
dimensionality. Here we show the practical direct measurement of a
high-dimensional state vector in the discrete basis of orbital-angular
momentum. Through weak measurements of orbital-angular momentum and strong
measurements of angular position, we measure the complex probability amplitudes
of a pure state with a dimensionality, d=27. Further, we use our method to
directly observe the relationship between rotations of a state vector and the
relative phase between its orbital-angular-momentum components. Our technique
has important applications in high-dimensional classical and quantum
information systems, and can be extended to characterize other types of large
quantum states.Comment: 8 pages, 3 figure
Angular two-photon interference and angular two-qubit states
Using angular-position-orbital-angular-momentum entangled photons, we study angular two-photon interference in a scheme in which entangled photons are made to pass through apertures in the form of double angular slits, and using this scheme, we demonstrate an entangled two-qubit state that is based on the angular-position correlations of entangled photons. The entanglement of the two-qubit state is quantified in terms of concurrence. These results provide an additional means for preparing entangled quantum states for use in quantum information protocols
Influence of Atmospheric Turbulence on Optical Communications using Orbital Angular Momentum for Encoding
We describe an experimental implementation of a free-space 11-dimensional
communication system using orbital angular momentum (OAM) modes. This system
has a maximum measured OAM channel capacity of 2.12 bits/photon. The effects of
Kolmogorov thin-phase turbulence on the OAM channel capacity are quantified. We
find that increasing the turbulence leads to a degradation of the channel
capacity. We are able to mitigate the effects of turbulence by increasing the
spacing between detected OAM modes. This study has implications for
high-dimensional quantum key distribution (QKD) systems. We describe the sort
of QKD system that could be built using our current technology.Comment: 6 pages, 5 figure
Measurement of the Orbital Angular Momentum Spectrum of Partially Coherent Fields using Double Angular Slit Interference
We implement an interferometric method using two angular slits to measure the
orbital angular momentum (OAM) mode spectrum of a partially coherent field. As
the angular separation of the slits changes, an interference pattern for a
particular OAM mode is obtained. The visibility of this interference pattern as
a function of angular separation is equivalent to the angular correlation
function of the field. By Fourier transforming the angular correlation function
obtained from the double angular slit interference, we are able to calculate
the OAM spectrum of the partially coherent field. This method has potential
application for characterizing the OAM spectrum in high-dimensional quantum
information protocols.Comment: 5 pages, 5 figure
Photon efficient wavefront sensing using an SLM for polarization-based weak measurements
A novel scheme is proposed for two dimensional direct measurement of wave functions using an SLM. This photon efficient method can be potentially useful for wavefront sensing of turbulence in adaptive optics systems used in free-space communication systems
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