Quantum weirdness in 'chicken or egg' paradox

September 03, 2018

The "chicken or egg" paradox was first proposed by philosophers in Ancient Greece to describe the problem of determining cause-and-effect.

Now, a team of physicists from The University of Queensland and the NÉEL Institute has shown that, as far as quantum physics is concerned, the chicken and the egg can both come first.

Dr Jacqui Romero from the ARC Centre of Excellence for Engineered Quantum Systems said that in quantum physics, cause-and-effect is not always as straightforward as one event causing another.

"The weirdness of quantum mechanics means that events can happen without a set order," she said.

"Take the example of your daily trip to work, where you travel partly by bus and partly by train.

"Normally, you would take the bus then the train, or the other way round.

"In our experiment, both of these events can happen first," Dr Romero said.

"This is called `indefinite causal order' and it isn't something that we can observe in our everyday life."

To observe this effect in the lab, the researchers used a setup called a photonic quantum switch.

UQ's Dr Fabio Costa said that with this device the order of events -- transformations on the shape of light -- depends on polarisation.

"By measuring the polarisation of the photons at the output of the quantum switch, we were able to show the order of transformations on the shape of light was not set."

"This is just a first proof of principle, but on a larger scale indefinite causal order can have real practical applications, like making computers more efficient or improving communication."

The research was published in Physical Reviews Letters by the American Physical Society.
-end-


University of Queensland

Related Quantum Physics Articles from Brightsurf:

Know when to unfold 'em: Applying particle physics methods to quantum computing
Borrowing a page from high-energy physics and astronomy textbooks, a team of physicists and computer scientists at Berkeley Lab has successfully adapted and applied a common error-reduction technique to the field of quantum computing.

Quantum physics: Physicists successfully carry out controlled transport of stored light
A team of physicists at Mainz University has successfully transported light stored in a quantum memory over a distance of 1.2 millimeters.

New system detects faint communications signals using the principles of quantum physics
Researchers at the National Institute of Standards and Technology (NIST) have devised and demonstrated a system that could dramatically increase the performance of communications networks while enabling record-low error rates in detecting even the faintest of signals.

Quirky response to magnetism presents quantum physics mystery
In a new study just published and highlighted as an Editor's Suggestion in Physical Review Letters, scientists describe the quirky behavior of one such magnetic topological insulator.

Evidence of power: Phasing quantum annealers into experiments from nonequilibrium physics
Scientists at Tokyo Institute of Technology (Tokyo Tech) use commercially available quantum annealers, a type of quantum computer, to experimentally probe the validity of an important mechanism from nonequilibrium physics in open quantum systems.

Adapting ideas from quantum physics to calculate alternative interventions for infection and cancer
Published in Nature Physics, findings from a new study co-led by Cleveland Clinic and Case Western Reserve University teams show for the first time how ideas from quantum physics can help develop novel drug interventions for bacterial infections and cancer.

Quantum physics: Realization of an anomalous Floquet topological system
An international team led by physicists from the Ludwig-Maximilians Universitaet (LMU) in Munich realized a novel genuine time-dependent topological system with ultracold atoms in periodically-driven optical honeycomb lattices.

Quantum physics provides a way to hide ignorance
Students can hide their ignorance and answer questions correctly in an exam without their lack of knowledge being detected by teachers -- but only in the quantum world.

Quantum physics: Physicists develop a new theory for Bose-Einstein condensates
Bose-Einstein condensates are often described as the fifth state of matter: At extremely low temperatures, gas atoms behave like a single particle.

Attosecond physics: Quantum brakes in molecules
Physicists have measured the flight times of electrons emitted from a specific atom in a molecule upon excitation with laser light.

Read More: Quantum Physics News and Quantum Physics Current Events
Brightsurf.com 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 Amazon.com.