Researchers use quantum entanglement to improve differential interference contrast microscopy

February 11, 2014 by Bob Yirka report
Illustration of (a) LCM-DIM and (b) the entanglement-enhanced microscope. The red and blue lines indicate horizontally and vertically polarized light. (c), (d) and (e) The change in the signal while the sample is scanned. Credit: arxiv.org/abs/1401.8075

(Phys.org)—A team of researchers with members from Hokkaido and Osaka Universities in Japan has used quantum entanglement of photons to improve image results created using differential interference contrast microscopy. In their paper published in Nature Communications, the team describes how they used entangled photons to enhance an image taken of an etched (to a depth of just 17 nanometers) letter "Q" on a glass plate, and how much improvement was observed.

Scientists have been using a type of microscope that relies on reading information from pairs of photons reflected off of a surface for several years. The difference between the information provided by each of the photons (the difference in phase) allows for creating an image. The result is stunningly sharp ultra-close-up images of three dimensional surfaces (such as microchips or microorganisms). Until now, however, the resolution of this type of microscopy—known as differential interference contrast microscopy—has been limited by the standard quantum limit—which is based on the Heisenberg uncertainty principle. Scientists have also known for some time that if entangled photons were used instead, they could bypass that limit and create images with better resolution. In this new effort, that's exactly what the researchers have done.

The reason that using entangled photons allow for more information is because measuring one gives information about the other, which results in more information obtained than from two un-entangled photons. The researchers tested this theory by replacing the part of the microscope that emits photons, with one that emitted —with it in place they etched the letter "Q" into a and then proceeded to create an image of it using their new and improved microscope. In so doing, they found an improved signal to noise ratio of 1.35—which can be seen by the naked eye when comparing photographs of the same etching done by both the new and old method.

(a) Atomic force microscope (AFM) image of a glass plate sample (BK7) on whose surface a ‘Q’ shape is carved in relief with an ultra-thin step using optical lithography. (b) The section of the AFM image of the sample, which is the area outlined in red in (a). The height of the step is estimated to be 17.3 nm from this data. (c) The image of the sample using an entanglement-enhanced microscope where two photon en- tangled state is used to illuminate the sample. (d) The image of the sample using single photons (a classical light source). Credit: arxiv.org/abs/1401.8075

Besides offering a way to create sharper images, the new technique might also prove useful for looking at material that is easily damaged by strong light—it might also lend itself to other types of measuring devices such as interferometers.

Explore further: Physics team entangles photons that never coexisted in time

More information: An entanglement-enhanced microscope, Nature Communications 4, Article number: 2426 DOI: 10.1038/ncomms3426 . On Arxiv: http://arxiv.org/abs/1401.8075

Abstract
Among the applications of optical phase measurement, the differential interference contrast microscope is widely used for the evaluation of opaque materials or biological tissues. However, the signal-to-noise ratio for a given light intensity is limited by the standard quantum limit, which is critical for measurements where the probe light intensity is limited to avoid damaging the sample. The standard quantum limit can only be beaten by using N quantum correlated particles, with an improvement factor of √N. Here we report the demonstration of an entanglement-enhanced microscope, which is a confocal-type differential interference contrast microscope where an entangled photon pair (N=2) source is used for illumination. An image of a Q shape carved in relief on the glass surface is obtained with better visibility than with a classical light source. The signal-to-noise ratio is 1.35±0.12 times better than that limited by the standard quantum limit.

Related Stories

Physics team entangles photons that never coexisted in time

May 28, 2013

(Phys.org) —Researchers at the Hebrew University of Jerusalem have succeeded in causing entanglement swapping between photons that never coexisted in time. In their paper published in the journal Physical Review Letters, ...

Chinese team entangles eight photons, breaking record

June 3, 2011

In a game of one-upmanship, a Chinese team of physicists has figured out how to entangle eight photons simultaneously and to observe them in action; the previous record was six. In a paper published in arXiv, the team from ...

Recommended for you

Carefully crafted light pulses control neuron activity

November 17, 2017

Specially tailored, ultrafast pulses of light can trigger neurons to fire and could one day help patients with light-sensitive circadian or mood problems, according to a new study in mice at the University of Illinois.

Strain-free epitaxy of germanium film on mica

November 17, 2017

Germanium, an elemental semiconductor, was the material of choice in the early history of electronic devices, before it was largely replaced by silicon. But due to its high charge carrier mobility—higher than silicon by ...

New imaging technique peers inside living cells

November 16, 2017

To undergo high-resolution imaging, cells often must be sliced and diced, dehydrated, painted with toxic stains, or embedded in resin. For cells, the result is certain death.

The stacked color sensor

November 16, 2017

Red-sensitive, blue-sensitive and green-sensitive color sensors stacked on top of each other instead of being lined up in a mosaic pattern – this principle could allow image sensors with unprecedented resolution and sensitivity ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.