In recent years, quantum computing has grown considerably and is a very active
field of research. Although the prototypes currently available are not yet
really practical, some institutions have already started to demonstrate the
computational potential of quantum computers. However, researchers still face
a major pitfall: stabilizing qubits in the face of background noise. And for
some experts, this problem might be impossible to solve.

It has been 40 years since physicist Richard Feynman identified that
quantum methods ought to be ready to perform a completely new type of
computation that outperforms even probably the most highly effective standard
computer systems. “Feynman argued that quantum computing should offer an
exponential speed-up for many classical computations,” says Cristian Calude at
the University of Auckland in New Zealand. And with a slew of breakthroughs,
quantum computer systems appear like they might now be hitting the large time.
Perhaps.

Because they’ve properties that simply don’t exist within the classical world,
quantum entities resembling atoms, photons, electrons and the like have entry
to a completely different set of routines for info processing if used to make
quantum bits, or qubits – a probably way more highly effective set.

### The computing power offered by qubits

Part of that’s down to quantum superposition, which implies a qubit can be
used to symbolize a complicated mixture of the 0 and 1 binary states
utilized in regular computing. That doesn’t imply it is 0 and 1 on the
identical time. A greater means to put it is that might prove to be 0 or 1.

Quantum algorithms use a course of known as “interference” to skew these
undefined properties and bias the interactions of a number of qubits in a
means that will increase the chance they’ll arrive at a ultimate state that
incorporates a resolution to the issue they’re making an attempt to resolve.

That’s the place entanglement comes into the combination. The spooky
connections between qubits it generates by some means enable for a sample of
interference the place the paths main to every incorrect answer destroy each
other and cancel out, whereas the paths main to the precise answer are
strengthened. In 2019, Google's quantum computing team announced that it had
achieved “quantum supremacy ”; that is, when a quantum processor performs
tasks that a conventional computer cannot.

Its 54-qubit Sycamore processor took just 3 minutes and 20 seconds to solve
a problem that would take 10,000 years to solve on the world's most powerful
conventional computer, the researchers said. That's not to say that Google's
quantum computer, or anyone else that has achieved quantum supremacy since,
is about to do anything useful. The problem Google solved was highly
esoteric. In May, Isaac Chuang of the Massachusetts Institute of Technology
(MIT), one of the world's leading authorities on quantum computing,
described the current state of the technology as a simple ad-generating
system.

### Stabilizing qubits: an extremely complex challenge

This brings us to the long journey ahead of a practical and useful machine.
The inconvenient truth is that in quantum computing, size matters. Qubits
containing data must retain their delicate quantum states for a long time
and not succumb to environmental influences such as heat and vibration that
can cause them to decoher, creating miscalculations.

This is a problem that can only be overcome by scaling. Current estimates
suggest that in large programmable quantum computers, most qubits - perhaps as
many as 5 out of 6 - will perform error correction, not a calculation. This
means that we'll need a million qubits before we can do anything really
useful. Keeping so many qubits cold enough or maintaining all of their quantum
states long enough to perform a computation is a monumental engineering
challenge.

It could take decades, but researchers are at least taking a few steps in
the right direction… IBM aims to build an 1,121-qubit machine by 2023, and
the company envisioned a colossal helium-cooled refrigerator to contain it.
Others, including Winfried Hensinger of the University of Sussex, UK, want
to avoid the complications of cooling: they are stepping up operations with
qubits of trapped ions that shuttle around a large circuit to perform
calculations.

### Noise and qubits: an impossible problem to solve?

Still others perform calculations by sending qubits of photons around a
silicon nitride chip that can be fabricated on a large scale using processes
already proven in the semiconductor industry. However, Gil Kalai, a
mathematician at the Hebrew University of Jerusalem in Israel, argued that
the basic noise level in a quantum computer will always be too high, no
matter how many qubits are available. "My analysis says that correcting
quality errors will not be possible."

Sabrina Maniscalco from the University of Helsinki in Finland is also
skeptical. “Finding a cure for the effect of environmental noise is not only,
in my opinion, a technological problem, but more conceptual and fundamental. I
would say that I am optimistic, rather than confident”.

## Via: NewScientist

Tags:
Physics