Scientists have
overcome a major hurdle facing quantum computing: How to protect quantum
information from degradation by the environment while simultaneously performing
computation in a solid-state quantum system. The research was reported in Nature.
A group led by the
United States Department of Energy’s Ames Laboratory physicist Viatsheslav
Dobrovitski and including scientists at Delft
University of Technology; the University
of California, Santa
Barbara; and University
of Southern California,
made this big step forward on the path to using the motions of single electrons
and nuclei for quantum information processing. The discovery opens the door to
robust quantum computation with solid-state devices and using quantum
technologies for magnetic measurements with single-atom precision at nanoscale.
Quantum
information processing relies on the combined motion of microscopic elements,
such as electrons, nuclei, photons, ions, or tiny oscillating joists. In
classical information processing, information is stored and processed in bits,
and the data included in each bit is limited to two values (0 or 1), which can
be thought of as a light switch being either up or down. But, in a quantum bit,
called a qubit, data can be represented by how these qubits orient and move in
relationship with each other, introducing the possibility for data expression
in many tilts and movements.
This power of
quantum information processing also poses a major challenge: even a minor “bump” off course causes qubits to lose data. And qubits tend to interact quite
sensitively with their environment, where multiple forces bump them off track.
But, because the
key to quantum information processing is in the relationship between qubits,
the solution is not as easy as isolating a single qubit from its environment.
“The big step
forward here is that we were able to decouple individual qubits from the
environment, so they retain their information, while preserving the coupling
between the qubits themselves” said Dobrovitski.
Solid-state hybrid systems are useful for
quantum information processing because they are made up of different types of
qubits that each perform different functions, much like different parts of a
car combine to move it down the road. In the case of Dobrovitski’s work, the
hybrid system includes magnetic moments of an electron and a nucleus.
“This type of hybrid system may be
particularly good for quantum information processing because electrons move
fast, can be manipulated easily, but they also lose quantum information
quickly. Nuclei move very slow, are difficult to manipulate, but they also
retain information well,” said Dobrovitski. “You can see an analogy between
this hybrid quantum system and the parts of a classical computer: the processor
works fast but doesn’t keep information long, while the memory works slowly but
stores information for a long time.”
Usually, when you decouple
qubits from their environment to protect their quantum data, you decouple them
from everything, even from each other.
