Featured Research

from universities, journals, and other organizations

Physicists Resolve Confounding Paradox Of Quantum Theory

Date:
January 15, 2009
Source:
University of Toronto
Summary:
University of Toronto quantum physicists Jeff Lundeen and Aephraim Steinberg have shown that Hardy's paradox, a proposal that has confounded physicists for over a decade, can be confirmed and ultimately resolved, a task which had seemingly been impossible to perform.

University of Toronto quantum physicists Jeff Lundeen and Aephraim Steinberg have shown that Hardy's paradox, a proposal that has confounded physicists for over a decade, can be confirmed and ultimately resolved, a task which had seemingly been impossible to perform.

Related Articles


"For nearly a century, the widespread interpretation of quantum mechanics suggests that everything is uncertain until it is observed, and that observation inevitably alters reality," says Professor Steinberg. "However, in the 1990s, a technique known as 'interaction-free measurement' seemed to promise the ability to 'see without looking,' as a Scientific American article put it at the time. But when Lucien Hardy proposed that one could never reliably make inferences about past events which hadn't been directly observed, a paradox emerged which suggested that whenever one attempted to reason about the past in this way they would be led into error."

Over the course of nearly two years of work, Steinberg and then-student Jeff Lundeen, now a research associate at the National Research Council of Canada, built a complicated quantum optical experiment and developed new theoretical tools. In essence, they combined Hardy's Paradox with a new theory known as weak measurement proposed by Tel Aviv University physicist Yakir Aharonov, showing that in one sense, one can indeed talk about the past, resolving the paradox. Weak measurement is a tool whereby the presence of a detector is less than the level of uncertainty around what is being measured, so that there is an imperceptible impact on the experiment. "We found that all of the seemingly paradoxical conclusions in Hardy's Paradox can, in fact, be experimentally verified," says Steinberg, "but that the use of weak measurement removes the contradiction."

"Until recently, it seemed impossible to carry out Hardy's proposal in practice, let alone to confirm or resolve the paradox," he says. "We have finally been able to do so, and to apply Aharonov's methods to the problem, showing that there is a way, even in quantum mechanics, in which one can quite consistently discuss past events even after they are over and done. Weak measurement finds what is there without disturbing it."

The research was funded with support from the Natural Sciences and Engineering Research Council of Canada, Quantum Works, the Canadian Institute for Photonic Innovations, and the Canadian Institute for Advanced Research.


Story Source:

The above story is based on materials provided by University of Toronto. Note: Materials may be edited for content and length.


Journal Reference:

  1. J.S. Lundeen and A.M. Steinberg. Experimental Joint Weak Measurement on a Photon Pair as a Probe of Hardy’s Paradox. Physical Review Letters, 2009; 102 (2): 020404 DOI: 10.1103/PhysRevLett.102.020404

Cite This Page:

University of Toronto. "Physicists Resolve Confounding Paradox Of Quantum Theory." ScienceDaily. ScienceDaily, 15 January 2009. <www.sciencedaily.com/releases/2009/01/090114141509.htm>.
University of Toronto. (2009, January 15). Physicists Resolve Confounding Paradox Of Quantum Theory. ScienceDaily. Retrieved December 22, 2014 from www.sciencedaily.com/releases/2009/01/090114141509.htm
University of Toronto. "Physicists Resolve Confounding Paradox Of Quantum Theory." ScienceDaily. www.sciencedaily.com/releases/2009/01/090114141509.htm (accessed December 22, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Monday, December 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Will New A350 Help Airbus Fly?

Will New A350 Help Airbus Fly?

Reuters - Business Video Online (Dec. 22, 2014) — Qatar Airways takes first delivery of Airbus' new A350 passenger jet. As Joel Flynn reports it's the planemaker's response to the Boeing 787 Dreamliner and the culmination of eight years of development. Video provided by Reuters
Powered by NewsLook.com
Man Parachutes Off Lawn Chair Airlifted By Helium Balloons

Man Parachutes Off Lawn Chair Airlifted By Helium Balloons

Buzz60 (Dec. 22, 2014) — A BASE jumper rides a lawn chair, a shotgun, and a giant bunch of helium balloons into the sky in what seems like a country version of the movie 'Up." Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Touch-Free Smart Phone Empowers Mobility-Impaired

Touch-Free Smart Phone Empowers Mobility-Impaired

Reuters - Innovations Video Online (Dec. 21, 2014) — A touch-free phone developed in Israel enables the mobility-impaired to operate smart phones with just a movement of the head. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com
Existing Chemical Compounds Could Revive Failing Antibiotics, Says Danish Scientist

Existing Chemical Compounds Could Revive Failing Antibiotics, Says Danish Scientist

Reuters - Innovations Video Online (Dec. 21, 2014) — A team of scientists led by Danish chemist Jorn Christensen says they have isolated two chemical compounds within an existing antipsychotic medication that could be used to help a range of failing antibiotics work against killer bacterial infections, such as Tuberculosis. Jim Drury went to meet him. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins