Characterizing super-semi sandwiches for quantum computing
Scientists develop a new technique to probe semiconductor-superconductor interactions

Date:
March 21, 2022
Source:
Institute of Science and Technology Austria
Summary:
Semiconductors are the foundation of modern technology while
superconductors with their zero electrical resistance could
become the basis for future technologies, including quantum
computers. So-called 'hybrid structures' -- carefully crafted
sandwiches made from superconductors and semiconductors -- may
lead to new quantum effects.

However, convincing observations have remained elusive. Now,
researchers have found a way to probe such 'super-semi sandwiches'
and to reveal what is going on.



FULL STORY ========================================================================== "There is an international race to identify the best platform for
controlling and processing quantum information for quantum computers,
where superconductors play a prominent role," says Duc Phan, PhD student
at the Institute of Science and Technology Austria (ISTA) and first author
of a new paper now published in Physical Review Letters. "Microsoft
is working on topological qubits using superconductor-semiconductor
sandwiches. However, before we can use them, we must understand the
fundamental physics behind them."

==========================================================================
Phan and his ISTA colleagues Jorden Senior and Andrew Higginbotham
from the Condensed Matter and Quantum Circuits group conducted this
study in close collaboration with partners from New York University and
with theory support from Areg Ghazaryan and Maksym Serbyn from ISTA's
Quantum Dynamics group. They developed a technique to probe the quantum interactions in super-semi sandwiches paving the way for new applications
like topological quantum bits based on so-called Majorana zero modes.

Cold Environment For their experiment, the researchers created a
microscopic sandwich made of an aluminium (Al) superconductor on top of
an indium-arsenic (InAs) semiconductor.

Superconductors are materials that have no electrical resistance. For that
to happen, they are cooled down to close to absolute zero temperature.

Semiconductors like InAs or silicon can be insulating or conduct
electricity depending on their environment and applied electric field.

Just like in a conventional sandwich that becomes more than the sum of
its parts, the combined properties of Al and InAs become modified in
super-semi sandwiches. At the interface between the Al superconductor and
the InAs semiconductor, the proximity effect spills the superconductivity
into the semiconductor creating new quantum states there. However,
until now researchers had a hard time studying them because they could
not be probed directly because of being concealed by a presence of the
Al superconducting layer.

"We found that by sending a current alternating billions of times a second through the vicinity of the sandwich, we could make the superconductor's
veil partially transparent and get feedback about the properties of the semiconductor," explains Senior. "We also applied a magnetic field to
create new quantum states we were looking for and developed a new model
that explained our observations." A new level of detail This first experimental result of the Higginbotham group since its establishment at
ISTA lays the groundwork to study superconductor-semiconductor hybrid structures at a new level of detail. "The parameters we can infer from
this could provide much-needed guidance to construct topological quantum
bits based on Majorana zero modes," says Jorden. He also highlights
that "ISTA is very well placed in this developing field because here experimental expertise, theoretical understanding, as well as excellent infrastructure provided by the state-of-the-art clean room -- the kitchen
for sandwich production -- come together." Phan and his colleagues are
excited about what insights they will gain with their novel probing
technique and what future applications may become possible once the
fundamental physics of this exotic sandwich has been understood.


========================================================================== Story Source: Materials provided by Institute_of_Science_and_Technology_Austria. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. D. Phan, J. Senior, A. Ghazaryan, M. Hatefipour,
W. M. Strickland,
J. Shabani, M. Serbyn, A. P. Higginbotham. Detecting
Induced p+/- ip Pairing at the Al-InAs Interface with a Quantum
Microwave Circuit.

Physical Review Letters, 2022; 128 (10) DOI: 10.1103/
PhysRevLett.128.107701 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220321103804.htm

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