/Reducing Errors In Two-Qubit Gates Bodes Well For Quantum Computing (via Qpute.com)

Reducing Errors In Two-Qubit Gates Bodes Well For Quantum Computing (via Qpute.com)


Most people in the tech world are well
aware of quantum computing. Sci-Tech
Daily
mentions that quantum computing utilizes the power of quantum mechanics to perform calculations
exponentially faster than the processors we currently have today. Quantum
computing uses elements smaller than an atom to complete its processes. The
tiniest component in a quantum circuit is known as a quantum bit or qubit. It
might seem like it’s easy to get quantum bits to interact since they should
just be like regular bitwise operators shrunk down. Unfortunately, the
microscopic world of quantum subatomic particles doesn’t work the same way as
the things we can see. That’s why there’s an entire field of research dedicated
to figuring this out.

Qubits function as quantum particles.
However, there’s an inherent error that seems to pop up when using certain
operations with qubits. The two-qubit gate problem has significant errors, and
since it’s such a fundamental part of quantum processing, that it throws a
wrench in the realization of this technological advancement. However, recent
research has found a way to significantly reduce those errors, so much so that
it may help to make for a more dependable quantum computing core. A paper published in the journal Physical Review X covers the details of
this remarkable achievement.

(a) Schematic diagram of a pairwise interacting three-body system. Each constituent body has anharmonic multiple energy level structure. (b),(c) Experimental realization of a three-body system in superconducting circuits. (d) Circuit schematic. In (c), false colors (blue, red, pink, green, and brown) are used to indicate the corresponding circuit components in (d).

The Problem Of Noise

When quantum buts are used for holding
and transferring data, there will always be an element of uncertainty. Qubits
are fragile mechanisms and can quickly become disturbed, a phenomenon known as
decoherence. When this phenomenon occurs, the qubits lose their quantum
mechanical behavior. In earlier experiments, the MIT team that made the
breakthrough experimented with tunable couplers. The supposition was that the
couplers could preserve the qubits’ fragile quantum state. Using the tuners to
switch the qubits on and off allowed them to be more resilient. This tunable
coupler advance seemed to be the right track, as many researchers agreed it
appeared to be helping with the issue of decoherence.

In quantum computing, gates can be
either one-qubit or two-qubit gates. The tunable couplers were excellent for
use with one-qubit gates, but errors showed up consistently when the two-qubit
gates were used. These resulted from residual interactions between both qubits
in the gate or either qubit and the coupler. Before using the coupler, these
errors were insignificant and could be safely ignored. Unfortunately, with the
use of the coupler, the issue becomes too pronounced to simply leave it be.
These errors are likely to increase exponentially with the scaling up of the
quantum computer into millions of qubits. The paper describes a way around that
two-qubit error.

Going All-In On Tunable
Couplers

So how did they fix the problem that,
admittedly, they introduced in the first place? Instead of reversing their
coupler idea and going back to ground zero, the MIT team decided to go all-in
on the coupler solution. The result was a 99.9% fidelity for calculations done
using the two most common two-qubit gates. This level of fidelity makes quantum
computing seem like an attainable goal now. In general terms, with higher
fidelity gates, there’s the potential for the qubit model to be scaled up. The
high fidelity translates into more reliable computation at higher scales.

The researchers utilized the coupler’s
higher energy levels to serve as a dampener. The energy level difference
canceled out the problematic interactions leaving the two-qubit gates with far
less error. As the researchers noted, better design and refinement of the
coupler are needed. While the current experimental state shows promise, the MIT
team thinks that couplers could be streamlined to reduce errors in two-qubit
gates even further. The next generation of quantum computers is likely to be
error-corrected. Additional qubits will be added to provide redundancy and
offer more robust solutions to problems. The answer to the two-qubit problem
opens the door to a jump in computing power. Redundancy only works if the gates
in question are sufficiently good. Without the couplers, the gates were not
good enough to introduce redundancy. With the couplers and this new fix, we may
actually see the evolution of quantum computing to the next level.

The Next Step May See An
Explosion in Computing Power

At current, most quantum computers
have minimal scope. In fact, a lot of their computing can be done on
traditional classical computers. The promise of quantum computing, as mentioned
before, is to solve complex problems that classical computers would not be able
to. The error issue with the building blocks of quantum computing (the qubit
gates) made realizing this dream untenable. However, this breakthrough may
provide the foundation needed to actually use quantum computers in the way they
were envisioned. This approach to the two-qubit error problem may be the most
significant quantum computing breakthrough to date. With the reliability
improved and redundancy in calculations the next step, we may soon see quantum
computers being used for more than just a narrow subset of problems.

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