Searching for quantum physics in all the right places

Jul 19, 2013
Searching for quantum physics in all the right places
A ‘quantum witness’ plot of the quantum state of a biological pigment–protein complex—the FMO complex from green sulfur bacteria. Positive values (blue to red) indicate that the system’s dynamics cannot be described classically, indicating that it is in a quantum state.

An improved method for measuring quantum properties offers new insight into the unique characteristics of quantum systems.

The properties of physical systems are fundamentally different to those of classical systems in a way that makes them attractive for applications such as computing and communications. However, it is often difficult to determine whether a system is in a quantum or classical physical state. Franco Nori and colleagues from the RIKEN Center for Emergent Matter Science, together with collaborators in Taiwan, have now developed a mechanism that permits the reliable detection of —even in complex systems1.

The unique behavior of quantum states arises from the of different states—a property known as quantum coherence. The physicist Erwin Schrödinger famously compared the concept of quantum coherence to a theoretical experiment in which a cat is sealed in a box with a vial of poison to be released by a random quantum mechanism. Without looking inside the box, it cannot be known whether the cat is dead or alive; the cat is therefore in a quantum coherent state. While some quantum states are used for computing, they also occur in nature—in certain , for example.

Measuring the properties of is important to further their technological utility. Unfortunately, existing measurement methods are impractical due to their complexity and the constraints they place on the quantum states that can be detected.

"Our main goal was to devise an unambiguous test that is easy and practical to implement, and which relies on as little 'foreknowledge' of the system as possible, to determine its quantum properties," explains Neill Lambert, a member of the research team.

The detection scheme developed by Nori, Lambert and colleagues involves the introduction of two 'quantum witnesses' that allow the comparison of two runs of an experiment: one in which the state of a system is observed twice, and one where it is only observed once. This procedure effectively sums the results of multiple random experiments to test whether there is any deviation from the expected classical values, which would provide evidence for a (Fig. 1). For Schrödinger's cat, such a deviation would suggest that the cat is neither dead nor alive but is instead in a quantum combination of both states.

Among the many possible quantum systems to which this method could be applied, experiments involving biological molecules are particularly interesting, says Nori. "The question of whether quantum coherence exists in biological organisms, for example in a photosynthetic complex, has triggered a surge of interest into the relationship between and biological function."

Explore further: Superabsorbing ring could make light work of snaps

More information: Scientific Reports 2, 885 (2012). DOI 10.1038/srep00885

Related Stories

New principle may help explain why nature is quantum

May 14, 2013

Like small children, scientists are always asking the question 'why?'. One question they've yet to answer is why nature picked quantum physics, in all its weird glory, as a sensible way to behave. Researchers ...

Playing quantum tricks with measurements

Feb 15, 2013

A team of physicists at the University of Innsbruck, Austria, performed an experiment that seems to contradict the foundations of quantum theory—at first glance. The team led by Rainer Blatt reversed a ...

Quantum algorithm breakthrough

Feb 24, 2013

An international research group led by scientists from the University of Bristol, UK, and the University of Queensland, Australia, has demonstrated a quantum algorithm that performs a true calculation for the first time. ...

Recommended for you

What is Nothing?

21 hours ago

Is there any place in the Universe where there's truly nothing? Consider the gaps between stars and galaxies? Or the gaps between atoms? What are the properties of nothing?

On the hunt for dark matter

23 hours ago

New University of Adelaide Future Fellow Dr Martin White is starting a research project that has the potential to redirect the experiments of thousands of physicists around the world who are trying to identify the nature ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

vacuum-mechanics
1 / 5 (6) Jul 19, 2013
The unique behavior of quantum states arises from the superposition of different states—a property known as quantum coherence. The physicist Erwin Schrödinger famously compared the concept of quantum coherence to a theoretical experiment in which a cat is sealed in a box with a vial of poison to be released by a random quantum mechanism.


Actually the concept of quantum superposition is due to the wave nature of quantum mechanics in which Erwin Schrödinger wave equation shows, however because we do not know – what the wave is. So this is the root problem, maybe this explanation could help….
http://www.vacuum...17〈=en