34 research outputs found
Real-Time Imaging of Quantum Entanglement
Quantum Entanglement is widely regarded as one of the most prominent features
of quantum mechanics and quantum information science. Although, photonic
entanglement is routinely studied in many experiments nowadays, its signature
has been out of the grasp for real-time imaging. Here we show that modern
technology, namely triggered intensified charge coupled device (ICCD) cameras
are fast and sensitive enough to image in real-time the effect of the
measurement of one photon on its entangled partner. To quantitatively verify
the non-classicality of the measurements we determine the detected photon
number and error margin from the registered intensity image within a certain
region. Additionally, the use of the ICCD camera allows us to demonstrate the
high flexibility of the setup in creating any desired spatial-mode
entanglement, which suggests as well that visual imaging in quantum optics not
only provides a better intuitive understanding of entanglement but will improve
applications of quantum science.Comment: Two supplementary movies available at the data conservancy projec
Automated Search for new Quantum Experiments
Quantum mechanics predicts a number of at first sight counterintuitive
phenomena. It is therefore a question whether our intuition is the best way to
find new experiments. Here we report the development of the computer algorithm
Melvin which is able to find new experimental implementations for the creation
and manipulation of complex quantum states. And indeed, the discovered
experiments extensively use unfamiliar and asymmetric techniques which are
challenging to understand intuitively. The results range from the first
implementation of a high-dimensional Greenberger-Horne-Zeilinger (GHZ) state,
to a vast variety of experiments for asymmetrically entangled quantum states --
a feature that can only exist when both the number of involved parties and
dimensions is larger than 2. Additionally, new types of high-dimensional
transformations are found that perform cyclic operations. Melvin autonomously
learns from solutions for simpler systems, which significantly speeds up the
discovery rate of more complex experiments. The ability to automate the design
of a quantum experiment can be applied to many quantum systems and allows the
physical realization of quantum states previously thought of only on paper.Comment: 5+8 pages, 4+1 figures (main text + supplementary
Azimuthal backflow in light carrying orbital angular momentum
M.V. Berry's work [J. Phys. A: Math. Theor. 43, 415302 (2010)] highlighted
the correspondence between backflow in quantum mechanics and superoscillations
in waves. Superoscillations refer to situations where the local oscillation of
a superposition is faster than its fastest Fourier component. This concept has
been used to demonstrate backflow in transverse linear momentum for optical
waves. In this work, we examine the interference of classical light carrying
only negative orbital angular momentum and observe in the dark fringes of such
an interference, positive local orbital angular momentum. This finding may have
implications for the studies of light-matter interaction and represents a step
towards observing quantum backflow in two dimensions.Comment: 8 pages, 5 figure