Tag Archives: Alex Lvovsky

Testing ‘Schroedinger’s cat’ on everyday objects at the University of Calgary (Canada)

For decades physicists have been grappling with the question of why the rules for quantum mechanics/physics are so different from classical physics while they try to unify the theories into one coherent explanation for why things are the way they are. At the same time, they’ve also been trying to test how the rules of quantum mechanics might apply to everyday objects and it seems a team from the University of Calgary (Alberta, Canada) have made a breakthrough.

The July 21, 2013 University of Calgary news release on EurekAlert provides an explanation of Schroedinger’s thought experiment (the dead/alive cat), quantum mechanics, and difficulties testing the theory on everyday objects thus helping those of us without that knowledge to better understand the breakthrough,

In contrast to our everyday experience, quantum physics allows for particles to be in two states at the same time — so-called quantum superpositions. A radioactive nucleus, for example, can simultaneously be in a decayed and non-decayed state.

Applying these quantum rules to large objects leads to paradoxical and even bizarre consequences. To emphasize this, Erwin Schroedinger, one of the founding fathers of quantum physics, proposed in 1935 a thought experiment involving a cat that could be killed by a mechanism triggered by the decay of a single atomic nucleus. If the nucleus is in a superposition of decayed and non-decayed states, and if quantum physics applies to large objects, the belief is that the cat will be simultaneously dead and alive.

While quantum systems with properties akin to ‘Schroedinger’s cat’ have been achieved at a micro level, the application of this principle to everyday macro objects has proved to be difficult to demonstrate.

“This is because large quantum objects are extremely fragile and tend to disintegrate when subjected to any interaction with the environment,” explains Lvovsky [professor Alex Lvovsky].

Now for the breakthrough (from the news release),

The breakthrough achieved by Calgary quantum physicists is that they were able to contrive a quantum state of light that consists of a hundred million light quanta (photons) and can even be seen by the naked eye. In their state, the “dead” and “alive” components of the “cat” correspond to quantum states that differ by tens of thousands of photons.

“The laws of quantum mechanics which govern the microscopic world are very different from classical physics that rules over large objects such as live beings,” explains lead author Lvovsky. “The challenge is to understand where to draw the line and explore whether such a line exists at all. Those are the questions our experiment sheds light on,” he states.

While the findings are promising, study co-author Simon [professor Christoph Simon] admits that many questions remain unanswered.

“We are still very far from being able to do this with a real cat,” he says. “But this result suggests there is ample opportunity for progress in that direction.”

They want to try this on a real live  cat? hmmm

For those who’d like to satisfy their curiosity further, here’s a link to and a citation for the published paper,

Observation of micro–macro entanglement of light by A. I. Lvovsky, R. Ghobadi, A. Chandra, A. S. Prasad & C. Simon. Nature Physics (2013) doi:10.1038/nphys2682 Published online 21 July 2013

This paper is behind a paywall.