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Industry News
Quantum Dots in Zinc Oxide Heterostructures
Quantum dots are tiny semiconductor structures
that can trap electrons in nanometre scale spaces
that allow scientists to control electron behaviour
and as such have recognised potential to serve as
qubits in quantum computing.
Research has mainly focused on gallium arsenide
and silicon, but now scientists at Tohuko University
have been investigating the possibility of using
zinc oxide, known for its strong electron correlation
and excellent spin quantum coherence, for use
in electrically defined quantum dots, that is those
created and controlled by electrical methods.
QUANTUM
DEVELOPMENTS
the photon dynamics followed key equations
Using Quantum Computers to magnetic field is present. fundamental to electromagnetism, including the
emulate Materials Hall Effect (a phenomenon of electrical conduction
On a superconducting quantum processor,
that arises in the presence of an electromagnetic
Researchers at the Massachusetts Institute of microwave photons move between qubits in a field), and that the synthetic electromagnetic field did
Technology (MIT) have developed a method of manner that resembles the electron hopping indeed accurately reflect the behaviour of a real field.
generating synthetic electromagnetic fields on between atoms, but, unlike electrons, they lack an
superconducting quantum processors, potentially electric charge, with the effect that their hopping Ilan Rosen, Lead Author and a postdoctoral
enabling quantum computers to emulate behaviour remains unchanged in a magnetic researcher at MIT, is quoted as follows:
materials. field. The team was unable to introduce a physical “ Quantum computers are powerful tools for The team manipulated the internal states of
magnetic field in their simulation, so techniques were quantum dots in zinc oxide using precise voltage
The technique, tested on a processor with 16 qubits, studying the physics of materials and other
devised to synthetically recreate the effects of it so as quantum mechanical systems. Our work enables control, which allowed the viewing of the Coulomb
allows scientists to experiment with material
to capture the intricate interactions between particles diamond, a key characteristic of quantum dots that
properties by simulating the behaviour of electrons us to simulate much more of the rich physics that
in a magnetic environment. has captivated material scientists. provides insights into the behaviour of the electrons
in an adjustable electromagnetic field. By precisely that are trapped inside. In addition, the Kondo
controlling the coupling between qubits, the In order to replicate the intricate hopping behaviour General purpose digital quantum simulators Effect, a quantum phenomenon whereby electron
team was able to successfully replicate the way that electromagnetic fields induce in electrons, hold tremendous promise, but they are still a interactions create conduction, was also observed.
electrons move within materials when influenced by the coupling between adjacent qubits in their long way off. Analogue simulation is another Importantly, with zinc oxide, the Kondo Effect was
electromagnetic forces. processor was adjusted by varying the microwave approach that may yield useful results in the observed even when the number of electrons in the
signals to each qubit, altering their energy levels. near term, particularly for studying materials. It
The ability to simulate electromagnetic fields is quantum dot did not fit the usual pattern.
Normally qubits are set to the same energy to
pivotal in being able to study a range of material is a straightforward and powerful application of
enable straightforward photon hopping, but for Tomohiro Otsuka, author of the paper and Associate
characteristics that are otherwise difficult to quantum hardware”.
this approach each qubit’s energy was modified to Professor at Tohoku University, explains:
replicate on quantum hardware. Now, it is possible
control how they interacted with each other. Senior Author and leader of the study, William D.
to investigate properties such as conductivity, Oliver, adds: “ The Coulomb diamond is like a fingerprint that
magnetisation, and polarisation, providing insights Through precise modulation of these energy levels, helps us identify the unique ‘personality’ of each
into the underlying physics of materials with photons were made to hop between qubits in a “ A nice feature of our emulator is that we need only quantum dot. By using zinc oxide, we’re opening
implications for electronics, such as enhanced complex pattern, Closely resembling the movement change the modulation amplitude or frequency to up new frontiers developing efficient and stable
semiconductors, insulators and superconductors. of electrons in a magnetic field. The ability to fine- mimic a different material system. In this way, we qubits, a cornerstone for quantum computing.
By carefully engineering the dynamics of qubits tune the microwave signals also allowed the team can scan over many material properties or model The Kondo Effect we observed is different from
and their interactions, scientists can emulate the to emulate a wide range of electromagnetic fields, parameters without having to physically fabricate what we typically see in other semiconductors
behaviour of electrons moving between atoms in each with unique strengths and distributions. The a new device each time”.
like gallium arsenide. This difference could help us
solid materials. process involved multiple rounds of experimentation Reference: Fowle, H., ‘Quantum Simulator to unlock new Electronic better understand electron behaviour in this new
to determine the optimal energy settings, modulation Materials’, Electronic Specifier, 13th. November
In real materials electrons exist in atomic orbitals and material and improve our ability to control and
strength and microwave frequency for each qubit.
when two atoms are close, their orbitals can overlap, manipulate qubits”.
allowing electrons to ‘hop’ between atoms. This Following the establishment of the correct
Reference: West, P., ‘A Pathway towards new Quantum Devices’,
hopping behaviour becomes more intricate when a parameters, the team was able to confirm that Electronic Specifier, 17th. December
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