Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Peeking into Schrodinger's box

21.01.2014
Measurement technology continues to show its potential for quantum information

Until recently measuring a 27-dimensional quantum state would have been a time-consuming, multistage process using a technique called quantum tomography, which is similar to creating a 3D image from many 2D ones.

Researchers at the University of Rochester have been able to apply a recently developed, alternative method called direct measurement to do this in a single experiment with no post-processing.

The work is of interest because fast, accurate and efficient methods for characterizing high-dimensional states like this could be central in developing high security quantum communications systems, as well as to probe our fundamental understanding of quantum mechanics.

The work was published this week in Nature Communications by a team of researchers from the University of Rochester and the University of Glasgow. In the paper they demonstrate direct measurements of the quantum state associated with the orbital-angular momentum.

"Our work shows that direct measurement offers an exciting alternative to quantum tomography," said Robert Boyd, Professor of Optics and Physics at the

University of Rochester and Canada Excellence Research Chair in Quantum Nonlinear Optics at the University of Ottawa. "As the field of quantum information continues to advance, we expect direct measurement to play an increasingly important role in this." Boyd added that although it is unclear exactly how much more efficient direct measurement is compared to quantum tomography, the lack of post-processing is a major factor in speeding-up direct measurements.

The direct measurement technique offers a way to directly determine the state of a quantum system. It was first developed in 2011 by scientists at the National Research Council Canada, who used it to determine the position and momentum of photons. Last year, a group of Rochester/Ottawa researchers led by Boyd showed that direct measurement could be applied to measure the polarization states of light. The new paper is the first time this method has been applied to a discrete, high dimensional system.

Such direct measurements of the wavefunction might have appeared to be ruled out by the uncertainty principle – the idea that certain properties of a quantum system could be known with precision only if other properties were known poorly. However, direct measurement involves a "trick" that makes it possible.

Direct measurements consists of two types of measurements performed one after the other, first a "weak" measurement followed by a "strong" measurement. In quantum mechanics the act of measuring a quantum state disturbs it irreversibly, a phenomenon referred to as collapse of the wavefunction. The trick lies with the first measurement being so gentle that it only slightly disturbs the system and does not cause the wavefunction to collapse.

"It is sort of like peeking into the box to see if Schrodinger's cat is alive, without fully opening the box," said lead author Dr. Mehul Malik, currently a post-doctoral research fellow at the University of Vienna and who was a Ph.D. in Boyd's group when the work was performed. "The weak measurement is essentially a bad measurement, which leaves you mostly uncertain about whether the cat is alive or dead. It does, however¬, give partial information on the health of the cat, which when repeated many times can lead to near certain information as to whether the cat is alive or dead." Malik adds that the beauty of the weak measurement is that it does not destroy the system, unlike most standard measurements of a quantum system, allowing a subsequent measurement—the "strong" measurement of the other variable.

This sequence of weak and strong measurements is then repeated for multiple identically prepared quantum systems, until the wave function is known with the required precision.

Ph.D. student Mohammad Mirhosseini was also part of the Rochester team. Other collaborators included Professor Miles Padgett and Martin Lavery from the University of Glasgow, UK, and Dr. Jonathan Leach, from Heriot-Watt University, Edinburgh, UK.

About the University of Rochester

The University of Rochester is one of the nation's leading private universities. Located in Rochester, N.Y., the University gives students exceptional opportunities for interdisciplinary study and close collaboration with faculty through its unique cluster-based curriculum. Its College, School of Arts and Sciences, and Hajim School of Engineering and Applied Sciences are complemented by its Eastman School of Music, Simon School of Business, Warner School of Education, Laboratory for Laser Energetics, School of Medicine and Dentistry, School of Nursing, Eastman Institute for Oral Health, and the Memorial Art Gallery.

Leonor Sierra | EurekAlert!
Further information:
http://www.rochester.edu

More articles from Physics and Astronomy:

nachricht Streamlining accelerated computing for industry
24.08.2016 | DOE/Oak Ridge National Laboratory

nachricht Lehigh engineer discovers a high-speed nano-avalanche
24.08.2016 | Lehigh University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Streamlining accelerated computing for industry

PyFR code combines high accuracy with flexibility to resolve unsteady turbulence problems

Scientists and engineers striving to create the next machine-age marvel--whether it be a more aerodynamic rocket, a faster race car, or a higher-efficiency jet...

Im Focus: X-ray optics on a chip

Waveguides are widely used for filtering, confining, guiding, coupling or splitting beams of visible light. However, creating waveguides that could do the same for X-rays has posed tremendous challenges in fabrication, so they are still only in an early stage of development.

In the latest issue of Acta Crystallographica Section A: Foundations and Advances , Sarah Hoffmann-Urlaub and Tim Salditt report the fabrication and testing of...

Im Focus: Piggyback battery for microchips: TU Graz researchers develop new battery concept

Electrochemists at TU Graz have managed to use monocrystalline semiconductor silicon as an active storage electrode in lithium batteries. This enables an integrated power supply to be made for microchips with a rechargeable battery.

Small electrical gadgets, such as mobile phones, tablets or notebooks, are indispensable accompaniments of everyday life. Integrated circuits in the interiors...

Im Focus: UCI physicists confirm possible discovery of fifth force of nature

Light particle could be key to understanding dark matter in universe

Recent findings indicating the possible discovery of a previously unknown subatomic particle may be evidence of a fifth fundamental force of nature, according...

Im Focus: Wi-fi from lasers

White light from lasers demonstrates data speeds of up to 2 GB/s

A nanocrystalline material that rapidly makes white light out of blue light has been developed by KAUST researchers.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

The energy transition is not possible without Geotechnics

25.08.2016 | Event News

New Ideas for the Shipping Industry

24.08.2016 | Event News

A week of excellence: 22 of the world’s best computer scientists and mathematicians in Heidelberg

12.08.2016 | Event News

 
Latest News

Spherical tokamak as model for next steps in fusion energy

25.08.2016 | Power and Electrical Engineering

Scientists identify spark plug that ignites nerve cell demise in ALS

25.08.2016 | Health and Medicine

Secure networks for the Internet of the future

25.08.2016 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>