Physicists breeding Schroedinger cat states

May 01, 2017

(Toronto - May 1, 2017) Physicists have learned how they could breed Schrödinger cats in optics. CIFAR Quantum Information Science Fellow Alexander Lvovsky led the team of Russian Quantum Center and University of Calgary scientists who tested a method that could potentially amplify superpositions of classical states of light beyond microscopic limits and help determine the boundaries between the quantum and classical worlds.

The study was published today in Nature Photonics.

In 1935, German physicist Erwin Schrödinger proposed a thought experiment where a cat, hidden from the observer, is in a superposition of two states: it was both alive and dead. Schrödinger's cat was intended to show how radically different the macroscopic world we see is from the microscopic world governed by the laws of quantum physics.

However, the development of quantum technologies makes it possible to create increasingly complex quantum states, and Schrödinger's thought experiment no longer seems too far out of reach.

"One of the fundamental questions of physics is the boundary between the quantum and classical worlds. Can quantum phenomena, provided ideal conditions, be observed in macroscopic objects? Theory gives no answer to this question -- maybe there is no such boundary. What we need is a tool that will probe it," says Lvovsky, who is a professor at the University of Calgary and head of the Quantum Optics Laboratory of the Russian Quantum Center, where the experiment was set up.

Exactly such a tool is provided by the physical analogue of the Schrödinger cat - an object in a quantum superposition of two states with opposite properties. In optics, this is a superposition of two coherent light waves where the fields of the electromagnetic waves point in two opposite directions at once. Until now, experiments could only obtain such superpositions at small amplitudes that limit their use. The Lvovsky group carried out the procedure of "breeding" such states, which makes it possible to obtain optical "cats" of higher amplitudes with greater success.

Co-author and University of Calgary graduate student Anastasia Pushkina explains: "The idea of the experiment was proposed in 2003 by the group of Professor Timothy Ralph of the University of Queensland, Australia. In essence, we cause interference of two "cats" on a beam splitter. This leads to an entangled state in the two output channels of that beam splitter. In one of these channels, a special detector is placed. In the event this detector shows a certain result, a "cat" is born in the second output whose energy is more than twice that of the initial one."

The Lvovsky group tested this method in the lab. In the experiment, they successfully converted a pair of negative squeezed "Schrodinger cats" of amplitude 1.15 to a single positive "cat" of amplitude 1.85. They generated several thousand such enlarged "cats" in their experiment.

"It is important that the procedure can be repeated: new 'cats' can, in turn, be overlapped on a beam splitter, producing one with even higher energy, and so on. Thus, it is possible to push the boundaries of the quantum world step by step, and eventually to understand whether it has a limit," says the first author of the study, a graduate student from the Russian Quantum Center and the Moscow State Pedagogical University, Demid Sychev.

Such macroscopic "Schrodinger cats" would have applications in quantum communication, teleportation and cryptography.

CIFAR creates knowledge that is transforming our world. Established in 1982, the Institute brings together interdisciplinary groups of extraordinary researchers from around the globe to address questions and challenges of importance to the world. Our networks help support the growth of research leaders and are catalysts for change in business, government and society. CIFAR is generously supported by the governments of Canada, British Columbia, Alberta, Ontario and Quebec, Canadian and international partners, as well as individuals, foundations and corporations.

Media contacts:

Alexander Lvovsky
CIFAR Quantum Information Science program
University of Calgary
Russian Quantum Center

Juanita Bawagan
Writer & Media Relations Specialist
+1 416-971-4884

Gloria Visser-Niven
Director, Marketing & Communications
Faculty of Science, University of Calgary
+1 403-220-7056

Anna Shangina
Russian Quantum Center
+7 985-270-5555

Canadian Institute for Advanced Research

Related Quantum Articles from Brightsurf:

Theoreticians show which quantum systems are suitable for quantum simulations
A joint research group led by Prof. Jens Eisert of Freie Universität Berlin and Helmholtz-Zentrum Berlin (HZB) has shown a way to simulate the quantum physical properties of complex solid state systems.

Quantum shake
There they were, in all their weird quantum glory: ultracold lithium atoms in the optical trap operated by UC Santa Barbara undergraduate student Alec Cao and his colleagues in David Weld's atomic physics group.

New evidence for quantum fluctuations near a quantum critical point in a superconductor
A study has found evidence for quantum fluctuations near a quantum critical point in a superconductor.

Quantum simulation of quantum crystals
International research team describes the new possibilities offered by the use of ultracold dipolar atoms

Quantum machines learn "quantum data"
Skoltech scientists have shown that quantum-enhanced machine learning can be used on quantum (as opposed to classical) data, overcoming a significant slowdown common to these applications and opening a ''fertile ground to develop computational insights into quantum systems''.

Simulating quantum 'time travel' disproves butterfly effect in quantum realm
Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no 'butterfly effect.' In the research, information--qubits, or quantum bits--'time travel' into the simulated past.

Orbital engineering of quantum confinement in high-Al-content AlGaN quantum well
Recently, professor Kang's group focus on the limitation of quantum confine band offset model, the hole states delocalization in high-Al-content AlGaN quantum well are understood in terms of orbital intercoupling.

Quantum classifiers with tailored quantum kernel?
Quantum information scientists have introduced a new method for machine learning classifications in quantum computing.

A Metal-like Quantum Gas: A pathbreaking platform for quantum simulation
Coherent and ultrafast laser excitation creates an exotic matter phase with spatially overlapping electronic wave-functions under nanometric control in an artificial micro-crystal of ultracold atoms.

Quantum leap: Photon discovery is a major step toward at-scale quantum technologies
A team of physicists at the University of Bristol has developed the first integrated photon source with the potential to deliver large-scale quantum photonics.

Read More: Quantum News and Quantum Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to