Electrical control of nuclear spin qubits: Important step towards quantum computers
Researchers of
Karlsruhe Institute of Technology (KIT) and their French partners
succeeded in making an important step towards quantum computers. Using a
spin cascade in single-molecule magnet, the scientists demonstrated how
nuclear spins can be manipulated with electric fields. Electric
manipulation allows for a quick and specific switching of quantum bits.
The experimental results are now reported in the journal Science.
One
of the most ambitious goals of nanotechnology is to realize a quantum
computer. Such a computer based on quantum mechanics principles is to
solve tasks much more efficiently than a classical computer. While the
latter works with bits that assume the value of zero or one, a quantum
computer uses so-called quantum bits, briefly referred to as qubits, as
smallest computation units. They may also assume values in between.
Qubits may rely on nuclear spins, i.e. intrinsic angular momentums of
atomic nuclei. They orient relative to a magnetic field in upward (up)
or downward (down) direction. Interlinkage of qubits with each other
results in mixed quantum states, on the basis of which many calculation
steps can be executed in parallel.
To integrate nuclear
spin-based qubits into electronic circuits and specifically trigger
novel information processes, specific electric manipulation of nuclear
spins is required. A team of scientists of the KIT and the Centre
National de la Recherche Scientifique (CNRS) in Grenoble and Strasbourg
recently succeeded for the first time in manipulating a single nuclear
spin in a purely electric manner. "Use of electric instead of magnetic
fields paves the way to addressing quantum states in conventional
electronic circuits," explains Professor Mario Ruben, Head of the
Molecular Materials Research Group of KIT's Institute of Nanotechnology
(INT). "There, quantum states can be manipulated specifically by
so-called displacement currents. Then, they can be directly read out
electronically."
For their experiments, the researchers used a
nuclear spin-qubit transistor that consists of a single-molecule magnet
connected to three electrodes (source, drain, and gate). The
single-molecule magnet is a TbPc2 molecule -- a single metal ion of
terbium that is enclosed by organic phthalocyanine molecules of carbon,
nitrogen, and hydrogen atoms. The gap between the electric field and the
spin is bridged by the so-called hyperfine-Stark effect that transforms
the electric field into a local magnetic field. This quantum mechanics
process can be transferred to all nuclear spin systems and, hence, opens
up entirely novel perspectives for integrating quantum effects in
nuclear spins into electronic circuits.
Posted By,
Divya.G AP/CSE
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