Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Quantum reality more complex than previously thought

Even an individual photon can travel along both arms of the interferometer at the same time. When it is unknown which path it is travelling along, we observe interference and the appearance of interference fringes. A strong signal is visible where the crests of light waves meet, and a weak signal is obtained at the meeting point of the troughs. If it is possible to determine which arm the photon travelled along, following leakage of information from the interferometer, the fringes disappear.

Credit: NLTK/Tentaris/Maciej Frolow
Even an individual photon can travel along both arms of the interferometer at the same time. When it is unknown which path it is travelling along, we observe interference and the appearance of interference fringes. A strong signal is visible where the crests of light waves meet, and a weak signal is obtained at the meeting point of the troughs. If it is possible to determine which arm the photon travelled along, following leakage of information from the interferometer, the fringes disappear.

Credit: NLTK/Tentaris/Maciej Frolow

Abstract:
Imagine you order a delivery of several glass vases in different colors. Each vase is sent as a separate parcel. What would you think of the courier if the parcels arrive apparently undamaged, yet when you open them, it turns out that all the red vases are intact and all the green ones are smashed to pieces? Physicists from the University of Warsaw and the Gdansk University of Technology have demonstrated that when quantum information is transmitted, nature can be as whimsical as this crazy delivery man.

Quantum reality more complex than previously thought

Warsaw, Poland | Posted on October 28th, 2013

Experiments on individual photons, conducted by physicists from the Faculty of Physics at the University of Warsaw (FUW) and the Faculty of Applied Physics and Mathematics at the Gdansk University of Technology (PG), have revealed yet another counterintuitive feature of the quantum world. When a quantum object is transmitted, its quantum property - whether it behaves as a wave or as a particle - appears to depend on other properties that at first glance have nothing to do with the transmission. These surprising results were published in the research journal Nature Communications.

Wave-interference experiments are some of the simplest and most elegant, and can be conducted by almost anyone. When a laser beam is directed at a plate with two slits, we observe a sequence of light and dark fringes. It has long been known that the fringes are visible even when just individual particles - single electrons or photons - pass through the slits. Physicists assume that every individual particle exhibits wave properties, passing through both slits at once and interfering with itself.

The situation is very different when it is possible to detect the path taken by a given photon or electron and determine which slit the particle has passed through, at least in principle. When information about the particle path leaks from the system to the observer, the interference disappears and instead of interference fringes no pattern is observed.

In order for photons to exhibit interference, their wavelengths must be the same, while electrons must have the same energy. However, quantum particles have a number of other properties. For example, they can be polarized (their electrical field vibrates in a certain plane) or have different spin orientations (a quantum property describing the dynamics of an object at rest).

"So far, it has been generally assumed that additional properties such as spin and polarization do not have a non-trivial impact on interference. We decided to study the topic in more depth, and we were surprised by the results we obtained," says Prof. Konrad Banaszek (FUW).

The experiments by physicists from the University of Warsaw and the Gdańsk University of Technology started by generating heralded photons. "The name sounds complicated, but the idea is simple in itself," according to Prof. Czeslaw Radzewicz (FUW). "We generate photons using a process in which they must be created in pairs. When we register one photon, we can be certain that the second was also born, and we know its properties such as direction or wavelength without destroying it. In other words, we use one photon to herald the generation of the second photon."

Each heralded photon was directed individually towards an interferometer, comprising two calcite crystals. In the first crystal, the photon was split and then sent through both arms of the interferometer at the same time. In each arm, researchers altered the polarization of the photon (the plane of vibration of its electrical field) by introducing noise. In the second calcite crystal, the paths were recombined to create a distinctive set of interference fringes, provided that the system did not leak any information as to which arm the given photon travelled along. The final stage of the experiment involved measuring the interference fringes using silicon avalanche photodiodes.

"It turned out that we were able to use measurements of interference fringes to determine how much information had leaked during transmission of the photon through the interferometer. In other words, we could be certain whether any eavesdropping had taken place during transmission," says Dr Michal Karpinski (University of Warsaw, currently University of Oxford), responsible for building the experimental system and conducting the measurements.

The results have revealed a new, surprising property of reality: the polarization of photons, or other internal degrees of freedom, play a highly non-trivial role in interference between the two paths.

"It is almost as though the quality of a courier delivery - for example, whether a glass vase delivered inside a securely packed parcel is still in one piece - depends on whether the vase is green or red. In our world the color has no bearing on whether the vase arrives intact or not. However, the condition of the parcels our 'quantum courier' delivers does indeed depend on internal properties that seem to have nothing to do with interference," according to Prof. Pawel Horodecki (PG).

The results allow physicists to examine the fundamental properties of reality in new, more comprehensive ways, as well as having practical applications in quantum cryptography. The Warsaw and Gdansk physicists have successfully derived a general inequality making it possible to precisely estimate the volume of information leaking from the measurement system.

###

The research was funded by the European Union 7th Framework Programme and as part of the Foundation for Polish Science TEAM Programme, co-financed from EU funds - the European Regional Development Fund.

####

About Faculty of Physics University of Warsaw
Physics and Astronomy first appeared at the University of Warsaw in 1816, under the then Faculty of Philosophy. In 1825 the Astronomical Observatory was established. Currently, the Faculty of Physics' Institutes include Experimental Physics, Theoretical Physics, Geophysics, Department of Mathematical Methods and an Astronomical Observatory. Research covers almost all areas of modern physics, on scales from the quantum to the cosmological. The Faculty's research and teaching staff includes ca. 200 university teachers, of which near 80 are employees with the title of professor. The Faculty of Physics, University of Warsaw, is attended by ca. 1000 students and more than 140 doctoral students.

For more information, please click here

Contacts:
Prof. Konrad Banaszek
Faculty of Physics, University of Warsaw
tel. +48 22 5532306


Prof. Pawel Horodecki
Faculty of Applied Physics and Mathematics, Gdansk University of Technology
tel. +48 58 3486069


Prof. Czeslaw Radzewicz
Faculty of Physics, University of Warsaw
tel. +48 22 5532243, +48 22 6254738


Dr Michal Karpinski
Department of Physics, University of Oxford
tel. +44 1865 273623

Copyright © Faculty of Physics University of Warsaw

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Faculty of Applied Physics and Mathematics, Gdansk University of Technology website:

Faculty of Physics at the University of Warsaw website:

Press Office for the Faculty of Physics at the University of Warsaw:

Related News Press

News and information

Innovation in Nanotechnology is Focus of Symposium: Annual event brings international experts to Northwestern Oct. 6 September 29th, 2016

Cambrios at CEATEC - Japan 2016 September 29th, 2016

Picosun patents ALD nanolaminate to prevent electronics from overheating September 28th, 2016

Leti and Taiwanese Tech Organizations Sponsoring Workshop in Taipei on MEMS, IoT, Smart Lighting Applications, System Reliability & Security September 28th, 2016

Physics

New breed of optical soliton wave discovered September 9th, 2016

NREL discovery creates future opportunity in quantum computing: Research into perovskites looks beyond material's usage for efficient solar cells September 9th, 2016

Location matters in the self-assembly of nanoclusters: Iowa State University scientists have developed a new formulation to explain an aspect of the self-assembly of nanoclusters on surfaces that has broad applications for nanotechnology September 8th, 2016

University of Akron researchers find thin layers of water can become ice-like at room temperature: Results could lead to an assortment of anti-friction solutions August 30th, 2016

Govt.-Legislation/Regulation/Funding/Policy

Crystalline Fault Lines Provide Pathway for Solar Cell Current: New tomographic AFM imaging technique reveals that microstructural defects, generally thought to be detrimental, actually improve conductivity in cadmium telluride solar cells September 26th, 2016

Tattoo therapy could ease chronic disease: Rice-made nanoparticles tested at Baylor College of Medicine may help control autoimmune diseases September 23rd, 2016

PHENOMEN is a FET-Open Research Project aiming to lay the foundations a new information technology September 19th, 2016

NIST Patents Single-Photon Detector for Potential Encryption and Sensing Apps September 16th, 2016

Quantum Computing

NREL discovery creates future opportunity in quantum computing: Research into perovskites looks beyond material's usage for efficient solar cells September 9th, 2016

NREL Discovery Creates Future Opportunity in Quantum Computing: Research into perovskites looks beyond materialís usage for efficient solar cells September 1st, 2016

Colors from darkness: Researchers develop alternative approach to quantum computing August 31st, 2016

Diamonds and quantum information processing on the nano scale August 31st, 2016

Discoveries

Fighting cancer with sticky nanoparticles September 27th, 2016

Gold nanoparticles conjugated quercetin inhibits epithelial-mesenchymal transition, angiogenesis and invasiveness via EGFR/VEGFR-2 mediated pathway in breast cancer September 27th, 2016

UNAM develops successful nano edible coating which increases life food September 27th, 2016

Crystalline Fault Lines Provide Pathway for Solar Cell Current: New tomographic AFM imaging technique reveals that microstructural defects, generally thought to be detrimental, actually improve conductivity in cadmium telluride solar cells September 26th, 2016

Announcements

Innovation in Nanotechnology is Focus of Symposium: Annual event brings international experts to Northwestern Oct. 6 September 29th, 2016

Cambrios at CEATEC - Japan 2016 September 29th, 2016

Picosun patents ALD nanolaminate to prevent electronics from overheating September 28th, 2016

Leti and Taiwanese Tech Organizations Sponsoring Workshop in Taipei on MEMS, IoT, Smart Lighting Applications, System Reliability & Security September 28th, 2016

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic