Quantum memory for communication networks of the future

Nov 08, 2010
The photo shows the experimental setup for a quantum information experiment. The table is filled with optical elements such as mirrors, lenses and wave plates, which are used to guide and manipulate infrared light. Inside each of the two metal cylinders is a glass cell with caesium atoms. The two cylinders are magnetic shields which protect the atoms from magnetic fields. Shown in the upper right corner is a pair of detectors which are used to make measurements of the infrared light. Credit: Quantop

Researchers from the Niels Bohr Institute at the University of Copenhagen have succeeded in storing quantum information using two 'entangled' light beams. Quantum memory or information storage is a necessary element of future quantum communication networks. The new findings are published in Nature Physics.

Quantum networks will be able to protect the security of information better than the current conventional communication networks. The cornerstone of quantum communication is a phenomenon called entanglement between two quantum systems, for example, two light beams. means that the two light beams are connected to each other, so that they have well defined common characteristics, a kind of common knowledge. A can – according to the laws of quantum mechanics, not be copied and can therefore be used to transfer data in a secure way.

In professor Eugene Polzik's research group Quantop at the Niels Bohr Institute researchers have now been able to store the two entangled light beams in two quantum memories. The research is conducted in a laboratory where a forest of mirrors and optical elements such as wave plates, beam splitters, lenses etc. are set up on a large table, sending the light around on a more than 10 meter long labyrinthine journey. Using the optical elements, the researchers control the light and regulate the size and intensity to get just the right wavelength and polarisation the light needs to have for the experiment.

The illustration shows the two quantum memories. Each memory consists of a glass cell filled with caesium atoms, which are shown as small blue and red balls. The light beam is sent through the atoms and the quantum information is thus transferred from the light to the atoms. Credit: Quantop

The two entangled light beams are created by sending a single blue through a crystal where the blue light beam is split up into two red light beams. The two red light beams are entangled, so they have a common quantum state. The quantum state itself is information.

The two light beams are sent on through the labyrinth of mirrors and optical elements and reach the two memories, which in the experiment are two glass containers filled with a gas of caesium atoms. The atoms' quantum state contains information in the form of a so-called spin, which can be either 'up' or 'down'. It can be compared with computer data, which consists of the digits 0 and 1. When the light beams pass the atoms, the quantum state is transferred from the two light beams to the two memories. The information has thus been stored as the new quantum state in the atoms.

"For the first time such a memory has been demonstrated with a very high degree of reliability. In fact, it is so good that it is impossible to obtain with conventional memory for light that is used in, for example, internet communication. This result means that a quantum network is one step closer to being a reality", explains professor Eugene Polzik.

Explore further: New research signals big future for quantum radar

More information: dx.doi.org/10.1038/NPHYS1819

Provided by University of Copenhagen

4.3 /5 (6 votes)

Related Stories

Physicists Demonstrate Three-Color Entanglement

Oct 07, 2009

(PhysOrg.com) -- For the first time, physicists have demonstrated the quantum entanglement of three light beams, all of different wavelengths. Entanglement of two light beams of different wavelengths has already ...

Quantum electronics: Two photons and chips

Jan 20, 2006

Scientists at Toshiba Research Europe Limited (Cambridge, UK) believe they are on to a way of producing entangled twins of photons using a simple semiconductor electronic device. Such a chip-based source of entangled photons ...

Shining light in quantum computing

Sep 12, 2006

University of Queensland scientist Devon Biggerstaff is investigating ways to manipulate light in a process that will help shape future supercomputers and communication technology.

Recommended for you

New filter could advance terahertz data transmission

2 hours ago

University of Utah engineers have discovered a new approach for designing filters capable of separating different frequencies in the terahertz spectrum, the next generation of communications bandwidth that ...

The super-resolution revolution

2 hours ago

Cambridge scientists are part of a resolution revolution. Building powerful instruments that shatter the physical limits of optical microscopy, they are beginning to watch molecular processes as they happen, ...

Precision gas sensor could fit on a chip

4 hours ago

Using their expertise in silicon optics, Cornell engineers have miniaturized a light source in the elusive mid-infrared (mid-IR) spectrum, effectively squeezing the capabilities of a large, tabletop laser onto a 1-millimeter ...

A new X-ray microscope for nanoscale imaging

5 hours ago

Delivering the capability to image nanostructures and chemical reactions down to nanometer resolution requires a new class of x-ray microscope that can perform precision microscopy experiments using ultra-bright ...

New research signals big future for quantum radar

16 hours ago

A prototype quantum radar that has the potential to detect objects which are invisible to conventional systems has been developed by an international research team led by a quantum information scientist at the University ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.