Optics: Statistics light the way

May 22, 2013
Optics: Statistics light the way
Pulses of low-level laser light trigger electrical responses of cells from the retina, which demonstrate these cells’ sensitivity to photon statistics. Credit: Comstock/Thinkstock

Millions of years of evolution have molded our eyes into highly sensitive optical detectors, surpassing even many man-made devices. Now, Leonid Krivitsky and his co-workers at the A*STAR Data Storage Institute and the A*STAR Institute of Medical Biology, Singapore, have shown that the photoreceptor cells found in the retina are even sensitive to the statistical properties of light. This ability could be harnessed in 'bioquantum' interfaces, a novel class of optical devices that use biological systems to detect the quantum nature of light.

Light comprises discrete bundles of energy known as photons. A 40-Watt light bulb, for example, creates more than 1019 (a one followed by 19 zeros) visible photons every second. Nevertheless, attenuated sources that generate light pulses containing just a few photons are also useful. In such ultralow-intensity light pulses, the of photons emitted in a single pulse depends on the light source.

Warm light sources such as light-bulb filaments generate photons in bunches. Lasers, in contrast, create photons randomly—each is emitted independently of the next. Krivitsky and his co-workers experimentally demonstrated that rod in the eye can distinguish between pulses of light from either a laser or a thermal light based only on these differing distributions. "Showing that such cells can assess photon statistics provides hope for accessing the of light using biodetectors," says Krivitsky.

Krivitsky and his team trapped a photoreceptor cell from a frog on the end of a suction pipette. Then they fired green-light laser pulses at the cell through an optical fiber. The same device could also imitate a thermal light source when they placed a rotating disk of ground glass and an aperture into the beam path.

They observed that rhodopsin molecules in the cell absorbed the incoming photons, which generated an ion current. The researchers amplified and measured this current as the average number of photons in each light pulse increased. They noticed a much sharper increase in detected current for the laser light than the pseudothermal pulses. This is because, while the average photon number is the same, an individual pseudothermal pulse was more likely to have a low number of photons. The photon distribution of the laser pulses, on the other hand, was much narrower.

The two types of photon emitters investigated in these experiments are examples of 'classical' light sources. "The next step is to investigate quantum light, such as pulses with a fixed number of photons," notes Krivitsky.

Explore further: Quantum optics with microwaves

More information: Sim, N., Cheng, M. F., Bessarab, D., Jones, C. M. & Krivitsky, L. A. Measurement of photon statistics with live photoreceptor cells. Physical Review Letters 109, 113601 (2012). dx.doi.org/10.1103/PhysRevLett.109.113601

add to favorites email to friend print save as pdf

Related Stories

Quantum optics with microwaves

May 08, 2013

(Phys.org) —Physicists at ETH Zurich have demonstrated one of the quintessential effects of quantum optics—known as the Hong-Ou-Mandel effect—with microwaves, whose frequency is 100'000 times lower ...

Switching with a few photons for quantum computing

Dec 05, 2012

(Phys.org)—Quantum computing, where bits of information, or "qubits," are represented by the state of single atomic particles or photons of light, won't be of much use unless we can read the results. Cornell ...

Recommended for you

High power laser sources at exotic wavelengths

Apr 14, 2014

High power laser sources at exotic wavelengths may be a step closer as researchers in China report a fibre optic parametric oscillator with record breaking efficiency. The research team believe this could ...

Combs of light accelerate communication

Apr 14, 2014

Miniaturized optical frequency comb sources allow for transmission of data streams of several terabits per second over hundreds of kilometers – this has now been demonstrated by researchers of Karlsruhe ...

User comments : 0

More news stories

CERN: World-record current in a superconductor

In the framework of the High-Luminosity LHC project, experts from the CERN Superconductors team recently obtained a world-record current of 20 kA at 24 K in an electrical transmission line consisting of two ...

Glasses strong as steel: A fast way to find the best

Scientists at Yale University have devised a dramatically faster way of identifying and characterizing complex alloys known as bulk metallic glasses (BMGs), a versatile type of pliable glass that's stronger than steel.

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.