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Scientific publications

The Institute for Quantum Computing (IQC) researchers continue to collaborate and publish their research with the top journals around the world.

The IQC Publications database provides access to scientific literature that has been authored or co-authored by IQC researchers.

Scientific highlights

IQC faculty, postdoctoral fellows and students continue to conduct internationally recognized quantum information science research. Here is a sampling of their cutting-edge research published in academic journals over the past term. 

Controlling orbital angular momentum of neutron waves

NATURE 525, 504–506 (24 September 2015)

An experiment by a team of researchers led by IQC shows, for the first time, that a wave property of neutrons, Orbital Angular Momentum (OAM), can be controlled by any specified value. This newfound control of neutron OAM states means that researchers can now use neutron OAM beams to see inside materials that optical, x-ray or electron OAM beams can’t penetrate. This control can help measure the magnetism, for example, in magnetic materials, as well as enable deeper probes of superconducting and chiral materials.

Research Assistant Professor DMITRY PUSHIN, a member of the Department of Physics at the University of Waterloo, and collaborator CHARLES CLARK of the Joint Quantum Institute in Maryland conceived of the idea to control neutron OAM. Pushin designed the experiment that uses neutrons created by a nuclear reactor at the National Institute of Standards and Technology (NIST) and passes them through a Mach-Zehnder interferometer.

Infinity is a bit closer

PHYS. REV. LETT. 115, 160505 – Published 15 October 2015

Mathematician David Hilbert proposed the Hilbert Hotel Paradox thought experiment in 1924 to demonstrate infinity – the mathematical notion of no limits. The researchers from the universities of Strathclyde, Glasgow, Rochester, Ottawa and IQC associated the rooms with quantum states and then looked for a way to vacate every second level, given that a quantum system that has an infinite amount of quantum states.

Physical Review Letters published the results in the paper Quantum Hilbert Hotel in October. IQC postdoctoral fellow FILIPPO MIATTO proposed the use of Orbital Angular Momentum (OAM) states of light to implement the Hilbert Hotel protocol. OAM is associated with the rotation of an object around a fixed axis and in the case of a light beam to the rotation of the optical phase around the direction of propagation.

By showing that they could physically realize the Hilbert Hotel Paradox, the researchers also found that they could perform deterministic non-linear interactions on the OAM by pre-sorting and then applying distinct Hilbert Hotel operation to the distinct OAM components. This opens up new possibilities for quantum information and computation operations.

Closing the loopholes

PHYS. REV. LETT. 115, 250402 – Published 16 December 2015

Researchers in Canada, the United States and Europe led by the National Institute of Standards and Technology in Boulder, Colorado and IQC alumnus KRISTER SHALM have ruled out classical theories of correlation with remarkably high precision. A group including IQC members EVAN MEYER-SCOTT, YANBAO ZHANG, THOMAS JENNEWEIN and alumnus DENY HAMEL built and performed an experiment that shows the world is not governed by local realism.

Local realism states that the world is predictable and only influenced by its immediate surroundings. Due to technological limitations, work by John Bell allowed scientists to experimentally test the hypothesis nature is governed by local realism through measuring entangled particles to find the strength of their correlations. Scientists had to make additional assumptions to show local realism was incompatible with their experimental results. This opened three possible loopholes – locality, freedom-of-choice and fair-sampling.

With new detectors built by NIST and a new high-performance photon source, researchers now have the technology needed to perform the Bell test and close all three loopholes simultaneously. The paper, A strong loophole-free test of local realism, appeared in Physical Review Letters in December. The results could have great significance for device-independent quantum communication. 

A proof-of-concept demonstration of quantum fingerprinting beats the best known classical proof

NATURE COMMUNICATIONS 6, 8735 (2015)

IQC researchers NORBERT LÜTKENHAUS, JUAN MIGUEL ARRAZOLA and SHIHAN SAJEED, in collaboration with researchers from the group of Professor HOI-KWONG LO at the University of Toronto, experimentally demonstrated a quantum fingerprinting system that can transmit less information than the best known classical protocol.

 In this problem, Alice and Bob receive inputs and based on these inputs, they send a message to a third party – the referee. The referee uses this received information to determine whether the inputs to Alice and Bob are equal, and the goal is to do this by transmitting as little information as possible. By modifying a version of a commercial Quantum Key Distribution (QKD) system using optical components, the researchers were able to transmit messages up to 100 Mbits with 66% less information than the best known classical protocol over a five-kilometre standard fibre operating at telecom wavelengths. Nature Communications published the results Experimental quantum fingerprinting with weak coherent pulses in October.