Featured Research

from universities, journals, and other organizations

An infallible quantum measurement

Date:
August 5, 2013
Source:
University of Innsbruck
Summary:
For quantum physicists, entangling quantum systems is one of their every day tools. Entanglement is a key resource for upcoming quantum computers and simulators. Now, physicists in Austria and Switzerland have developed a new, reliable method to verify entanglement in the laboratory using a minimal number of assumptions about the system and measuring devices.

The new method allows for reliable statements about the entanglement in a system.
Credit: Uni Innsbruck/Ritsch

For quantum physicists, entangling quantum systems is one of their every day tools. Entanglement is a key resource for upcoming quantum computers and simulators. Now, physicists in Innsbruck, Austria and Geneva, Switzerland have developed a new, reliable method to verify entanglement in the laboratory using a minimal number of assumptions about the system and measuring devices. Hence, this method witnesses the presence of useful entanglement.

Related Articles


Their findings on this 'verification without knowledge' has been published in Nature Physics.

Quantum computation, quantum communication and quantum cryptography often require entanglement. For many of these upcoming quantum technologies, entanglement -- this hard to grasp, counter-intuitive aspect in the quantum world -- is a key ingredient. Therefore, experimental physicists often need to verify entanglement in their systems. "Two years ago, we managed to verify entanglement between up to 14 ions," explains Thomas Monz. He works in the group of Rainer Blatt at the Institute for Experimental Physics, University Innsbruck. This team is still holding the world-record for the largest number of entangled particles. "In order to verify the entanglement, we had to make some, experimentally calibrated, assumptions. However, assumptions, for instance about the number of dimensions of the system or a decent calibration, make any subsequently derived statements vulnerable," explains Monz. Together with Julio Barreiro, who recently moved on the Max Planck Institute of Quantum Optics in Garching, and Jean-Daniel Bancal from the group of Nicolas Gisin at the University of Geneva, now at the Center for Quantum Technologies in Singapore, the physicists derived and implemented a new method to verify entanglement between several objects.

Finding correlations

The presented device-independent method is based on a single assumption: "We only have to make sure that we always apply the same set of operations on the quantum objects, and that the operations are independent of each other," explains Julio Barreiro. "However, which operations we apply in detail -- this is something we do not need to know." This approach -- called Device Independent -- allows them to get around several potential sources of error, and subsequently wrong interpretations of the results. "In the end, we investigate the correlations between the settings and the obtained results. Once the correlations exceed a certain threshold, we know that the objects are entangled." For the experimentally hardly avoidable crosstalk of operations applied to levitating calcium ions in the vacuum chamber in Innsbruck, the Swiss theorist Jean-Daniel Bancal managed to adapt the threshold according to a worst-case scenario. "When this higher threshold is breached, we can claim entanglement in the system with high confidence," states Bancal.

Assumptions as Achilles heel

For physicists, such procedures that are based on very few assumptions are highly interesting. By being basically independent of the system, they provide high confidence and strengthen the results of experimentalists. "Assumptions are always the Achilles heel -- be that for lab data or theory work," stresses Thomas Monz. "We managed to reduce the number of assumption to verify entanglement to a minimum. Our method thus allows for reliable statements about the entanglement in a system." In the actual implementation, the physicists in Innsbruck could verify entanglement of up to 6 ions. This new method can also be applied for larger systems. The technical demands, however, also increase accordingly.


Story Source:

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


Journal Reference:

  1. Julio T. Barreiro, Jean-Daniel Bancal, Philipp Schindler, Daniel Nigg, Markus Hennrich, Thomas Monz, Nicolas Gisin, Rainer Blatt. Demonstration of genuine multipartite entanglement with device-independent witnesses. Nature Physics, 2013; DOI: 10.1038/NPHYS2705

Cite This Page:

University of Innsbruck. "An infallible quantum measurement." ScienceDaily. ScienceDaily, 5 August 2013. <www.sciencedaily.com/releases/2013/08/130805092318.htm>.
University of Innsbruck. (2013, August 5). An infallible quantum measurement. ScienceDaily. Retrieved November 29, 2014 from www.sciencedaily.com/releases/2013/08/130805092318.htm
University of Innsbruck. "An infallible quantum measurement." ScienceDaily. www.sciencedaily.com/releases/2013/08/130805092318.htm (accessed November 29, 2014).

Share This


More From ScienceDaily



More Matter & Energy News

Saturday, November 29, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Magnetic Motors, Not Cables, Power This Elevator

Magnetic Motors, Not Cables, Power This Elevator

Newsy (Nov. 28, 2014) — Imagine an elevator without cables. ThyssenKrupp has drafted an elevator concept that would cruise on linear magnetic motors. Video provided by Newsy
Powered by NewsLook.com
NASA's First 3-D Printer In Space Creates Its First Object

NASA's First 3-D Printer In Space Creates Its First Object

Newsy (Nov. 26, 2014) — The International Space Station is now using a proof-of-concept 3D printer to test additive printing in a weightless, isolated environment. Video provided by Newsy
Powered by NewsLook.com
Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Bolivian Recycling Initiative Turns Plastic Waste Into School Furniture

Reuters - Innovations Video Online (Nov. 26, 2014) — Innovative recycling project in La Paz separates city waste and converts plastic garbage into school furniture made from 'plastiwood'. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Blu-Ray Discs Getting Second Run As Solar Panels

Blu-Ray Discs Getting Second Run As Solar Panels

Newsy (Nov. 26, 2014) — Researchers at Northwestern University are repurposing Blu-ray movies for better solar panel technology thanks to the discs' internal structures. Video provided by Newsy
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