Quantum communication: How to outwit noise

March 29, 2017

Nowadays we communicate via radio signals and send electrical pulses through long cables. This could change soon, however: Scientists have been working intensely on developing methods for quantum information transfer. This would enable tap-proof data transfer or, one day, even the linking of quantum computers.

Quantum information transfer requires reliable information transfer from one quantum system to the other, which is extremely difficult to achieve. Independently, two research teams -- one at the University of Innsbruck and the other at TU Wien (Vienna) -- have now developed a new quantum communication protocol. This protocol enables reliable quantum communication even under the presence of contaminating noise. Both research groups work with the same basic concept: To make the protocol immune to the noise, they add an additional element, a so-called quantum oscillator, at both ends of the quantum channel.

Reliable data transfer

Scientists have conducted quantum communication experiments for a long time. "Researchers presented a quantum teleportation protocol already in the 1990s. It permits transferring the state of one quantum system to another by using optical photons," says Benoit Vermersch, Postdoc in Peter Zoller's group at the University of Innsbruck. This works also over great distances but one has to accept that a lot of the photons are lost and only a tiny fraction reaches the detector.

"Our goal was to find a way to reliably transfer a quantum state from one place to the other without having to do it several times to make it work," explains Peter Rabl from the Atominstitut, TU Wien.Superconducting qubits, in particular, are promising elements for future quantum technologies. They are tiny circuits that can assume two different states at the same time. Contrary to conventional light switches that can be either turned on or turned off, the laws of quantum physics allow a qubit to assume any combination of these states, which is called quantum superposition.

To transfer this quantum state from one superconducting qubit to another requires microwave photons, which are already used for classic signal transfer. Reliably transferring quantum information via a microwave regime has been considered impossible as the constant thermal noise completely superposes the weaker quantum signal.

New transfer protocol

The two research groups have now shown that these obstacles are not impossible to overcome as previously assumed. In collaboration with teams from Harvard and Yale (USA) they have been able to develop a transfer protocol that is immune to the inevitable noise. "Our approach is to add another quantum system -- a microwave oscillator -- as a mediator at both ends of the protocol to couple the qubits instead of coupling them directly to the microwave channel or waveguide," explains Rabl.

"We cannot prevent the thermal noise that develops in the quantum channel," says Benoit Vermersch. "What is important is that this noise affects both oscillators on both ends in the same way. Therefore, we are able to exactly separate the detrimental effect of the noise from the weaker quantum signal through precise coupling to the waveguide."

"According to our calculations, we may connect qubits over several hundred meters with this protocol," says Peter Rabl. "We would still have to cool the channels but in the long term it will be technologically feasible to link buildings or even cities in a quantum physical manner via microwave channels."

Further information:

Prof. Peter Rabl
Institute for Atomic and Subatomic Physics
TU Wien
Stadionallee 2, 1020 Vienna
T: +43-1-58801-141830
peter.rabl@tuwien.ac.at

Dr. Benoit Vermersch
Institute for Theoretical Physics
University of Innsbruck
Technikerstraße 25, 6020 Innsbruck
T: +43 512 507 52259
benoit.vermersch@uibk.ac.at

Vienna University of Technology

Related Quantum State Articles from Brightsurf:

Theoreticians show which quantum systems are suitable for quantum simulations
A joint research group led by Prof. Jens Eisert of Freie Universit├Ąt Berlin and Helmholtz-Zentrum Berlin (HZB) has shown a way to simulate the quantum physical properties of complex solid state systems.

State gun laws may help curb violence across state lines: study
Columbia University Mailman School of Public Health researchers find that strong state firearm laws are associated with fewer firearm homicides--both within the state where the laws are enacted and across state lines.

Scientists find evidence of exotic state of matter in candidate material for quantum computers
Using a novel technique, scientists working at the Florida State University-headquartered National High Magnetic Field Laboratory have found evidence for a quantum spin liquid, a state of matter that is promising as a building block for the quantum computers of tomorrow.

Opioid prescriptions for knee surgery vary widely from state to state
New research from Texas A&M University and the University of Pennsylvania on opioid prescribing practices across the country after outpatient knee surgeries found that prescription strength and number of tablets is prescribed highest in Oklahoma and lowest in Vermont.

New evidence for quantum fluctuations near a quantum critical point in a superconductor
A study has found evidence for quantum fluctuations near a quantum critical point in a superconductor.

Quantum machines learn "quantum data"
Skoltech scientists have shown that quantum-enhanced machine learning can be used on quantum (as opposed to classical) data, overcoming a significant slowdown common to these applications and opening a ''fertile ground to develop computational insights into quantum systems''.

Simulating quantum 'time travel' disproves butterfly effect in quantum realm
Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no 'butterfly effect.' In the research, information--qubits, or quantum bits--'time travel' into the simulated past.

Quantum physicists crack mystery of 'strange metals,' a new state of matter
Strange metals are just plain odd. They are related to high-temperature superconductors and have surprising connections to the properties of black holes.

Orbital engineering of quantum confinement in high-Al-content AlGaN quantum well
Recently, professor Kang's group focus on the limitation of quantum confine band offset model, the hole states delocalization in high-Al-content AlGaN quantum well are understood in terms of orbital intercoupling.

The spin state story: Observation of the quantum spin liquid state in novel material
The quantum spin liquid (QSL) state is an exotic state of matter where the spin of electrons, which generally exhibits order at low temperatures, remains disordered.

Read More: Quantum State News and Quantum State Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.