Nav: Home

Quantum cats are hard to see

December 16, 2011

Are there parallel universes? And how will we know? This is one of many fascinations people hold about quantum physics. Researchers from the universities of Calgary and Waterloo in Canada and the University of Geneva in Switzerland have published a paper this week in Physical Review Letters explaining why we don't usually see the physical effects of quantum mechanics.

"Quantum physics works fantastically well on small scales but when it comes to larger scales, it is nearly impossible to count photons very well. We have demonstrated that this makes it hard to see these effects in our daily life," says Dr. Christoph Simon, who teaches in the Department of Physics and Astronomy at the University of Calgary and is one of the lead authors of the paper entitled: Coarse-graining makes it hard to see micro-macro entanglement.

It's well known that quantum systems are fragile. When a photon interacts with its environment, even just a tiny bit, the superposition is destroyed. Superposition is a fundamental principle of quantum physics that says that systems can exist in all their possible states simultaneously. But when measured, only the result of one of the states is given.

This effect is known as decoherence, and it has been studied intensively over the last few decades. The idea of decoherence as a thought experiment was raised by Erwin Schrödinger, one of the founding fathers of quantum physics, in his famous cat paradox: a cat in a box can be both dead and alive at the same time.

But, according to the authors of this study, it turns out that decoherence is not the only reason why quantum effects are hard to see. Seeing quantum effects requires extremely precise measurements. Simon and his team studied a concrete example for such a "cat" by using a particular quantum state involving a large number of photons.

"We show that in order to see the quantum nature of this state, one has to be able to count the number of photons in it perfectly," says Simon. "This becomes more and more difficult as the total number of photons is increased. Distinguishing one photon from two photons is within reach of current technology, but distinguishing a million photons from a million plus one is not."

University of Calgary

Related Quantum Physics Articles:

In atomic propellers, quantum phenomena can mimic everyday physics
In molecules there are certain groups of atoms that are able to rotate.
Testing quantum field theory in a quantum simulator
Quantum field theories are often hard to verify in experiments.
Diamonds coupled using quantum physics
Researchers at TU Wien have succeeded in coupling the specific defects in two such diamonds with one another.
Quantum physics offers insight into music expressivity
Scientists at Queen Mary University of London (QMUL) are bringing us closer to understanding the musical experience through a novel approach to analysing a common musical effect known as vibrato.
More than 100,000 people challenge Einstein in a unique worldwide quantum physics experiment
On Nov. 30, more than 100,000 people participated in the BIG Bell Test, a global experiment to test the laws of quantum physics.
Quantum physicist Carl M. Bender wins 2017 Dannie Heineman Prize for Mathematical Physics
The American Institute of Physics (AIP) and the American Physical Society (APS) announced today, on behalf of the Heineman Foundation for Research, Educational, Charitable, and Scientific Purposes, that Carl M.
USC quantum computing researchers reduce quantum information processing errors
USC Viterbi School of Engineering scientists found a new method to reduce the heating errors that have hindered quantum computing.
PPPL applies quantum theory and Einstein's special relativity to plasma physics issues
Researchers at the US Department of Energy's Princeton Plasma Physics Laboratory have developed a theory of plasma waves that can infer these properties in greater detail than in standard approaches.
Quantum satellite device tests technology for global quantum network
Researchers at the National University of Singapore and University of Strathclyde, UK, report first data from a satellite that is testing technology for a global quantum network.
An experiment seeks to make quantum physics visible to the naked eye
Predictions from quantum physics have been confirmed by countless experiments, but no one has yet detected the quantum physical effect of entanglement directly with the naked eye.

Related Quantum Physics Reading:

Quantum Mechanics: The Theoretical Minimum
by Leonard Susskind (Author), Art Friedman (Author)

From the bestselling author of The Theoretical Minimum, a DIY introduction to the math and science of quantum mechanics.
First he taught you classical mechanics. Now, physicist Leonard Susskind has teamed up with data engineer Art Friedman to present the theory and associated mathematics of the strange world of quantum mechanics.

In this follow-up to the New York Times best-selling The Theoretical Minimum, Susskind and Friedman provide a lively introduction to this famously difficult field, which attempts to understand the behavior of sub-atomic objects... View Details

Quantum Physics: A Beginner's Guide (Beginner's Guides)
by Alastair Rae (Author)

From quarks to computing, this fascinating introduction covers every element of the quantum world in clear and accessible language. Drawing on a wealth of expertise to explain just what a fascinating field quantum physics is, Rae points out that it is not simply a maze of technical jargon and philosophical ideas, but a reality which affects our daily lives. View Details

Quantum Physics: What Everyone Needs to Know®
by Michael G. Raymer (Author)

Around 1900, physicists started to discover particles like electrons, protons, and neutrons, and with these discoveries believed they could predict the internal behavior of the atom. However, once their predictions were compared to the results of experiments in the real world, it became clear that the principles of classical physics and mechanics were far from capable of explaining phenomena on the atomic scale. With this realization came the advent of quantum physics, one of the most important intellectual movements in human history. Today, quantum physics is everywhere: it explains how our... View Details

Reality Is Not What It Seems: The Journey to Quantum Gravity
by Carlo Rovelli (Author), Simon Carnell (Translator), Erica Segre (Translator)

“The man who makes physics sexy . . . the scientist they’re calling the next Stephen Hawking.” The Times Magazine

From the New York Times–bestselling author of Seven Brief Lessons on Physics, a closer look at the mind-bending nature of the universe.

What are the elementary ingredients of the world? Do time and space exist? And what exactly is reality? Theoretical physicist Carlo Rovelli has spent his life exploring these questions. He tells us how our understanding of reality has changed over the centuries and how physicists think... View Details

The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory
by Brian Greene (Author)

The international bestseller that inspired a major Nova special and sparked a new understanding of the universe, now with a new preface and epilogue.

Brian Greene, one of the world's leading string theorists, peels away layers of mystery to reveal a universe that consists of eleven dimensions, where the fabric of space tears and repairs itself, and all matter―from the smallest quarks to the most gargantuan supernovas―is generated by the vibrations of microscopically tiny loops of energy. The Elegant Universe makes some of the most sophisticated... View Details

Quantum Enigma: Physics Encounters Consciousness
by Bruce Rosenblum (Author), Fred Kuttner (Author)

In trying to understand the atom, physicists built quantum mechanics, the most successful theory in science and the basis of one-third of our economy. They found, to their embarrassment, that with their theory, physics encounters consciousness. Authors Bruce Rosenblum and Fred Kuttner explain all this in non-technical terms with help from some fanciful stories and anecdotes about the theory's developers. They present the quantum mystery honestly, emphasizing what is and what is not speculation. Quantum Enigma's description of the experimental quantum facts, and the quantum theory explaining... View Details

The Physics of God: Unifying Quantum Physics, Consciousness, M-Theory, Heaven, Neuroscience and Transcendence
by Joseph Selbie (Author), Amit Goswami (Foreword)

Setting aside the pervasive material bias of science and lifting the obscuring fog of religious sectarianism reveals a surprisingly clear unity of science and religion. The explanations of transcendent phenomena given by saints, sages, and near-death experiencers--miracles, immortality, heaven, God, and transcendent awareness--are fully congruent with scientific

discoveries in the fields of relativity, quantum physics, medicine, M-theory, neuroscience, and quantum biology.

The Physics of God describes the intersections of science and religion with colorful,... View Details

Introduction to Quantum Mechanics
by David J. Griffiths (Author)

This bestselling undergraduate quantum mechanics textbook is now available in a re-issued, affordable edition from Cambridge University Press. The text first teaches students how to do quantum mechanics, and then provides them with a more insightful discussion of what it means. The author avoids the temptation to include every possible relevant topic, instead presenting students with material that they can easily focus on in a complete treatment with few distractions and diversions. Fundamental principles are covered, quantum theory is presented, and special techniques are developed for... View Details

How to Teach Quantum Physics to Your Dog
by Chad Orzel (Author)

When physics professor Chad Orzel went to the pound to adopt a dog, he never imagined Emmy. She wasn’t just a friendly mutt who needed a home. Soon she was trying to use the strange ideas of quantum mechanics for the really important things in her life: chasing critters, getting treats, and going for walks. She peppered Chad with questions: Could she use quantum tunneling to get through the neighbor’s fence and chase bunnies? What about quantum teleportation to catch squirrels before they climb out of reach? Where are all the universes in which Chad drops steak on the floor?

With... View Details

The Quantum Labyrinth: How Richard Feynman and John Wheeler Revolutionized Time and Reality
by Paul Halpern (Author)

The story of the unlikely friendship between the two physicists who fundamentally recast the notion of time and history
In 1939, Richard Feynman, a brilliant graduate of MIT, arrived in John Wheeler's Princeton office to report for duty as his teaching assistant. A lifelong friendship and enormously productive collaboration was born, despite sharp differences in personality. The soft-spoken Wheeler, though conservative in appearance, was a raging nonconformist full of wild ideas about the universe. The boisterous Feynman was a cautious physicist who believed only what could be... View Details

Best Science Podcasts 2017

We have hand picked the best science podcasts for 2017. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Simple Solutions
Sometimes, the best solutions to complex problems are simple. But simple doesn't always mean easy. This hour, TED speakers describe the innovation and hard work that goes into achieving simplicity. Guests include designer Mileha Soneji, chef Sam Kass, sleep researcher Wendy Troxel, public health advocate Myriam Sidibe, and engineer Amos Winter.
Now Playing: Science for the People

#448 Pavlov (Rebroadcast)
This week, we're learning about the life and work of a groundbreaking physiologist whose work on learning and instinct is familiar worldwide, and almost universally misunderstood. We'll spend the hour with Daniel Todes, Ph.D, Professor of History of Medicine at The Johns Hopkins University, discussing his book "Ivan Pavlov: A Russian Life in Science."