Quantum antennae enable the exchange of quantum information between two separate memory cells located on a computer chip. Credit: Harald Ritsch |
The Austrian research group led by physicist Rainer Blatt
suggests a fundamentally novel architecture for quantum computation. They have
experimentally demonstrated quantum antennae, which enable the exchange of
quantum information between two separate memory cells located on a computer
chip. This offers new opportunities to build practical quantum computers.
Six years ago scientists at the Univ. of Innsbruck
realized the first quantum byte—a quantum computer with eight entangled quantum
particles; a record that still stands. “Nevertheless, to make practical use of
a quantum computer that performs calculations, we need a lot more quantum
bits,” says Prof. Rainer Blatt, who, with his research team at the Institute
for Experimental Physics, created the first quantum byte in an electromagnetic
ion trap. “In these traps we cannot string together large numbers of ions and
control them simultaneously.” To solve this problem, the scientists have
started to design a quantum computer based on a system of many small registers,
which have to be linked. To achieve this, Innsbruck
quantum physicists have now developed a revolutionary approach based on a
concept formulated by theoretical physicists Ignacio Cirac and Peter Zoller. In
their experiment, the physicists electromagnetically coupled two groups of ions
over a distance of about 50 micrometers. Here, the motion of the particles
serves as an antenna. “The particles oscillate like electrons in the poles of a
TV antenna and thereby generate an electromagnetic field,” explains Blatt. “If one
antenna is tuned to the other one, the receiving end picks up the signal of the
sender, which results in coupling.” The energy exchange taking place in this
process could be the basis for fundamental computing operations of a quantum
computer.
Antennae amplify
transmission
“We implemented this new concept in a very simple way,” explains Rainer Blatt.
In a miniaturized ion trap a double-well potential was created, trapping the
calcium ions. The two wells were separated by 54 micrometers. “By applying a
voltage to the electrodes of the ion trap, we were able to match the
oscillation frequencies of the ions,” says Blatt. “This resulted in a coupling
process and an energy exchange, which can be used to transmit quantum
information.” A direct coupling of two mechanical oscillations at the quantum
level has never been demonstrated before. In addition, the scientists show that
the coupling is amplified by using more ions in each well. “These additional
ions function as antennae and increase the distance and speed of the
transmission,” says Rainer Blatt, who is excited about the new concept. This
work constitutes a promising approach for building a fully functioning quantum
computer. “The new technology offers the possibility to distribute
entanglement. At the same time, we are able to target each memory cell
individually,” explains Rainer Blatt. The new quantum computer could be based
on a chip with many micro traps, where ions communicate with each other through
electromagnetic coupling. This new approach represents an important step
towards practical quantum technologies for information processing.
The quantum researchers are supported by the Austrian
Science Fund FWF, the European Union, the European Research Council, and the
Federation of Austrian Industries Tyrol.
