Tech Briefs Magazine - April 2024 - 37

Quantum Computing Architecture May Enable
High-Fidelity Communication
New quantum computing architecture could be used to connect large-scale devices.
Massachusetts Institute of Technology, Cambridge, MA
M
IT researchers have developed a
quantum computing architecture
that aims to enable extensible, high-fidelity
communication between superconducting
quantum processors.
The work, published in Nature Physics,
demonstrates step one - the deterministic
emission of single photons, information
carriers, in a user-specified direction. The
method ensures quantum information
flows in the correct direction more than 96
percent of the time. Linking several of
these modules enables a larger network of
interconnected quantum processors.
" Quantum interconnects are a crucial
step toward modular implementations of
larger-scale machines built from smaller
individual components, " said Bharath
Kannan, PhD, co-lead author of the research
paper. " The ability to communicate
between smaller subsystems will enable a
modular architecture for quantum processors,
and this may be a simpler way of scaling
to larger system sizes compared to the
brute-force approach of using a single
large and complicated chip. "
A quantum network links processing
nodes using photons that travel through
special
interconnects known as waveguides,
which either be unidirectional,
moving a photon only left or right, or it
can be bidirectional.
" We can get rid of these lossy components
if we have a waveguide that can support
propagation in both the left and right
directions, and a means to choose the direction
at will. This 'directional transmission' is
what we demonstrated, and it is the first
step toward bidirectional communication
with much higher fidelities, " said Kannan.
To accomplish this, the researchers built
a module comprising four qubits. The
technique involves preparing the two qubits
in an entangled state of single excitation
- a Bell state. This quantum-mechanical
state comprises two aspects: the
left qubit being excited and the right qubit
being excited. Both aspects exist simultaneously,
but which qubit is excited at a given
time is unknown.
Tech Briefs, April 2024
This image shows a module composed of superconducting qubits that can be used to directionally
emit microwave photons. (Image: Krantz NanoArt)
" The photon has a certain frequency, a
certain energy, and you can prepare a module
to receive it by tuning it to the same
frequency, " said co-lead author Aziza Almanakly,
Graduate student at MIT. " If they are
not at the same frequency, then the photon
will just pass by. It's analogous to tuning a
radio to a particular station. If we choose
the right radio frequency, we'll pick up the
music transmitted at that frequency. "
" The work demonstrates an on-demand
quantum emitter, in which the interference
of the emitted photon from an entanwww.techbriefs.com
gled
state defines the direction, beautifully
manifesting the power of waveguide quantum
electrodynamics, " said Yasunobu Nakamura,
Director of the RIKEN Center for
Quantum Computing. " It can be used as a
fully programmable quantum node that
can emit/absorb/pass/store quantum information
on a quantum network and as
an interface for a bus connecting multiple
quantum computer chips. "
For more information, contact Abby
Abazorius at abbya@mit.edu; 617-2532709.
37

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