MOSCOW, Oct. 11, 2019 /PRNewswire/ -- Scientists from
NUST MISIS sucessfully launched Russia's first prototype of a quantum
computer. The device working on two qubits performed a specific
quantum algorithm, exceeding the previously known accuracy limit by
3%. Superconducting materials were taken as the basis for
qubits.
Work on the creation of a quantum computer within the framework
of Russian Foundation for Advanced Research Projects has been
carried out at the NISU MISIS since 2016 under the supervision of
Valery Ryazanov, the chief
researcher of the University's Laboratory for Superconducting
Metamaterials. The design involves the use of superconducting
materials as the basis for qubits.
Qubits (quantum bits) are the "heart" of a quantum computer, an
analogue of the bits of a regular PC, but far more advanced. If PC
"thinks" and counts in zeros and ones, that is, each bit of
information can be encoded either as "0" or as "1", then the qubit
has the property of the so-called superposition, the ability to be
in both states simultaneously. This opens up great prospects,
because with such computing resources a quantum computer will be
able to considerably overtake the most powerful computing
devices.
A quantum computer based on superconducting materials is a more
advanced system than its counterparts. For example, other
scientific teams are developing qubits on individual atoms (which
can be "lost" due to a negligible size) and on ions (they can be
ordered only linearly, which is physically inconvenient). The
qubits created at NUST MISIS are made of aluminum, have a size of
300 microns. They cannot be "lost", and it is possible to order
them non-linearly.
During the experiment, a two-qubit quantum computer solved
Grover's quantum algorithm. Ideally, a quantum computer, thanks to
the superposition, can find the correct value x in solving this
problem in one call to the function f (x) with a probability of
100%.
"Grover's two-qubit algorithm is a very important step
towards creating a quantum computer. We are not the first in the
world to demonstrate its solution, but here we are talking
primarily about technological achievement. We have shown the
possibility of implementing all the necessary logical operations
for a universal quantum processor: initialization, single-qubit and
two-qubit operations, and reading, and with an innacuracy level
satisfactory for small algorithms," said Ilya Besedin, an engineer at the Laboratory for
Superconducting Metamaterials, one of the project
participants.
The biggest difficulty in creating a useful quantum processor is
errors. Unlike regular computers, which can work for years and
always produce reproducible and predictable results, quantum
computers are affected by noise, which distorts the calculation
results. Despite the fact that the two-qubit processor created at
NUST MISIS is too small to solve applied problems, it successfully
"overcame" the threshold of 50% probability of a correct answer,
reaching 53%.
The whole algorithm consists of initializing two qubits, four
one-qubit operations, two two-qubit operations, and reading two
qubits; errors in any of them reduces the probability of a correct
answer.
A chip for a quantum computer was manufactured at Bauman Moscow
State Technical University. The design of the algorithm and the
launch of the device was done at NUST MISIS, where a unique set of
equipment with cryostats was built in the Laboratory for
Superconducting Metamaterials, allowing operation at extremely low
temperatures to -273.14 degrees Celsius, which is close to absolute
zero.
"Nevertheless, we still have a long way to go," adds
Ilya Besedin. More recently,
an article by Google, which was not yet officially published,
appeared in press, stating that Google managed to implement the
"quantum superiority" algorithm on a 53-qubit superconducting
quantum processor. The task of "quantum superiority" is the most
favorable task for a quantum computer, which is very difficult to
accomplish on a classical computer. And if our overcoming of the
"classic" limit is still a fundamental result, the Google result is
already closer to the practical side: they were able to formulate
and solve a task that their processor can complete in minutes, and
a powerful supercomputer has been tested for weeks."
And even so, Google has not yet managed to make quantum computer
solving some practically useful task more effectively than a
classical one. However, now theoretical predictions regarding the
computational superiority of quantum computers are confirmed by
experiments.
The next important steps towards creating a useful quantum
computer are a demonstration of reduced to several tens of qubits
versions of "useful" quantum algorithms (for example, a simulator
of a chemical reaction or the ground state of a molecule) and a
demonstration of quantum error correction. Exactly for error
correction, by the way, superconducting qubits are best suited:
they can be organized into a two-dimensional lattice with local
interactions and parallel gates, which is necessary for the
"surface code", the simplest in terms of requirements and accuracy
of operations.
"We also want to move in this direction, but from my point of
view in quantum computing we should do not only "more", but also
"better ": the superconducting qubits that we use now turn out to
be quite expensive and give a lot of mistakes. And before doing
hundreds and thousands of qubits, in my opinion, it's worth working
on the most basic unit, a qubit", summarizes
Ilya Besedin.
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