Nav: Home

2000 atoms in two places at once

October 01, 2019

The quantum superposition principle has been tested on a scale as never before in a new study by scientists at the University of Vienna in collaboration with the University of Basel. Hot, complex molecules composed of nearly two thousand atoms were brought into a quantum superposition and made to interfere. By confirming this phenomenon - "the heart of quantum mechanics", in Richard Feynman's words - on a new mass scale, improved constraints on alternative theories to quantum mechanics have been placed. The work will be published in Nature Physics.

Quantum to classical?

The superposition principle is a hallmark of quantum theory which emerges from one of the most fundamental equations of quantum mechanics, the Schrödinger equation. It describes particles in the framework of wave functions, which, much like water waves on the surface of a pond, can exhibit interference effects. But in contrast to water waves, which are a collective behavior of many interacting water molecules, quantum waves can also be associated with isolated single particles.

Perhaps the most elegant example of the wave nature of particles is the double-slit experiment, in which a particle's wave function simultaneously passes through two slits and interferes. This effect has been demonstrated for photons, electrons, neutrons, atoms and even molecules, and it raises a question that physicists and philosophers have struggled with since the earliest days of quantum mechanics: how do these strange quantum effects transition into the classical world with which we are all familiar

Experimental approach

The experiments by Markus Arndt and his team at the University of Vienna approach this question in the most direct way possible, that is, by showing quantum interference with ever more massive objects. The molecules in the recent experiments have masses greater than 25,000 atomic mass units, several times larger than the previous record. One of the largest molecules sent through the interferometer, C707H260F908N16S53Zn4, is composed of more than 40,000 protons, neutrons, and electrons, with a de Broglie wavelength that is a thousand times smaller than the diameter of even a single hydrogen atom. Marcel Mayor and his team at the University of Basel used special techniques to synthesize such massive molecules that were sufficiently stable to form a molecular beam in ultra-high vacuum. Proving the quantum nature of these particles also required a matter-wave interferometer with a two-meter long baseline that was purpose-built in Vienna.

Alternative quantum models and macroscopicity

One class of models which aims to reconcile the apparent transition from a quantum to a classical regime predicts that the wave function of a particle spontaneously collapses with a rate proportional to its mass squared. By experimentally showing that a superposition is maintained for a heavy particle for a given length of time therefore directly places bounds on how often and how localized such a collapse process can be. In these experiments the molecules remained in a superposition for more than 7 ms, long enough to set new interferometric bounds on alternative quantum models.

A generalized measure called macroscopicity is used to classify just how well alternative models are ruled out by such experiments, and the experiments of Fein et al. published in Nature Physics indeed represent an order of magnitude increase in macroscopicity. "Our experiments show that quantum mechanics, with all its weirdness, is also amazingly robust, and I'm optimistic that future experiments will test it on an even more massive scale," says Fein. The line between quantum and classical is getting blurrier all the time.
-end-
Publication in Nature Physics

"Quantum superposition of molecules beyond 25 kDa", Y. Y. Fein, P. Geyer, P. Zwick, F. Kia?ka, S. Pedalino, M. Mayor, S. Gerlich, and M. Arndt, Nat. Phys. (2019). doi: 10.1038/s41567-019-0663-9; https://www.nature.com/articles/s41567-019-0663-9

University of Vienna

Related Quantum Mechanics Articles:

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.
Understanding mechanics and materials though evolution and biomaterials
Studying the evolution of bodily processes millions of years ago as well as the properties of today's biomaterials could improve soft robotics design and inform materials science research.
USTC realizes the first quantum-entangling-measurements-enhanced quantum orienteering
Researchers enhanced the performance of quantum orienteering with entangling measurements via photonic quantum walks.
A convex-optimization-based quantum process tomography method for reconstructing quantum channels
Researchers from SJTU have developed a convex-optimization-based quantum process tomography method for reconstructing quantum channels, and have shown the validity to seawater channels and general channels, enabling a more precise and robust estimation of the elements of the process matrix with less demands on preliminary resources.
What a pair! Coupled quantum dots may offer a new way to store quantum information
Researchers at the National Institute of Standards and Technology (NIST) and their colleagues have for the first time created and imaged a novel pair of quantum dots -- tiny islands of confined electric charge that act like interacting artificial atoms.
In leap for quantum computing, silicon quantum bits establish a long-distance relationship
In an important step forward in the quest to build a quantum computer using silicon-based hardware, researchers at Princeton have succeeded in making possible the exchange of information between two qubits located relatively far apart -- about the length of a grain of rice, which is a considerable distance on a computer chip.
Artificial intelligence algorithm can learn the laws of quantum mechanics
Artificial intelligence can be used to predict molecular wave functions and the electronic properties of molecules.
A new quantum data classification protocol brings us nearer to a future 'quantum internet'
A new protocol created by researchers at the Universitat Autònoma de Barcelona sorts and classifies quantum data by the state in which they were prepared, with more efficiency than the equivalent classical algorithm.
Bridge between quantum mechanics and general relativity still possible
An international team of researchers developed a unified framework that would account for this apparent break down between classical and quantum physics, and they put it to the test using a quantum satellite called Micius.
'Poor man's qubit' can solve quantum problems without going quantum
Researchers have built and demonstrated the first hardware for a probabilistic computer, a possible way to bridge the gap between classical and quantum computing.
More Quantum Mechanics News and Quantum Mechanics Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

TED Radio Wow-er
School's out, but many kids–and their parents–are still stuck at home. Let's keep learning together. Special guest Guy Raz joins Manoush for an hour packed with TED science lessons for everyone.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.