Quantum
computing has been a speculative subject that was originally developed
as just an idea. More commonly known as an area belonging to quantum
mechanics, quantum computing is really a promising fusion of concepts
from physics, mathematics and computer science. Why promising? Let's
find out.
Does the term quantum computing make you feel like it's
one of those things that you may not easily understand? Well, you're
not entirely mistaken. It is a subtle and complex subject, difficult to
explain and the fact that it's a relatively new field of study perhaps,
makes it even more incomprehensible. In extremely simple terms, quantum
computing has the potential to speed up computations (as if the
classical computers were not fast enough) to an unbelievable extent
leading to an exponential advance in processing power. Why do we need
such unimaginable speed and processing power? At some point in life, we
have either watched a movie or some sci-fi TV series where the good guys
need to hack into a computer network and stop the bad guys from blowing
up the world or some such evil act. Now there's a time bomb ticking
away to its last moments and our good guys need to guess the password
and they need to guess it fast before they're blown up! A quantum
computer would be heaven-sent for this scenario. This is perhaps, a
farfetched application for a quantum computer but breaking ciphers at
jet-speed is definitely one of its promising uses.
Making Sense of the Word "Quantum"
In
order to have quantum computing explained, we need to delve a little
into quantum mechanics. Quantum mechanics is based on the principle that
every object is made of quantum particles or quanta (atoms, electrons
and photons). These particles, sometimes, behave as waves and sometimes
the waves behave as particles, but really they are neither, unless
someone observes it. In addition, what the observer finds is well, a
random probability! Sounds bizarre? Well, hang in there. The quanta can
exist in the two states simultaneously! This is called the superposition
principle in quantum theory which finds application in quantum
computing. Another counter-intuitive quantum principle states that there
exists a strong correlation between quanta even when they're separated
by vast distances, even if they're at opposite ends of the universe!
This is the entanglement principle. Welcome to the quirky world of
quantum mechanics.
How do Quantum Computers Work?
If the
above paragraph didn't make much sense, perhaps this one will. A
classical computer uses bits to encode information, representing either
one or zero, while a quantum computer uses qubits. So with reference to
the above paragraph, a qubit can represent a one, a zero or a
superposition of these simultaneously, thus achieving quantum
parallelism. From this, we understand that a qubit can essentially
represent significantly more information than a bit in a classical
computer.
Quantum computing began as an idea that if the
principles of quantum mechanics could be represented by building a
quantum computer, computing could be revolutionized. Richard Feynman, a
Nobel prize winning physicist is considered one of the pioneers in the
field of quantum computing. He thought up the idea of a quantum computer
in 1982. In 1994, Peter Shor, a scientist with Bell Labs, devised an
algorithm that could be used to factor huge numbers especially products
of prime factors, using a quantum computer. However, this was again a
theoretical attempt as there was no actual quantum computer built to
test the algorithm.
Early Challenges in Building a Quantum Computer
Although
quantum computers have since been built, especially in the last few
years, the pioneers in this field had some real challenges in attempting
to build them. While several algorithms were written for a hypothetical
quantum computer, the counter-intuitive principles on which it was
based ironically posed the biggest challenge in realizing an actual
physical device. Maintaining the coherence of the quantum states proved
to be most difficult. Quantum parallelism could be achieved only when
the quantum states could be preserved/controlled for a certain desired
duration. External environmental factors (including the act of measuring
a quantum state, classical noise and quantum noise, etc.) were known to
cause quantum decoherence and all subsequent research in the field of
quantum computers began focusing on controlling or removing decoherence
by isolating these external factors.
Devices to Control Quantum Decoherence
Ion Traps and Optical Traps: Elongated electrodes form an
electromagnetic field to trap ions, curbing the potential for the atoms
to swerve. Ion trap devices have also been fabricated on chips. Optical
traps apply light waves to control particles.
Superconducting Qubits: These allow electrons to flow with least resistance at low temperatures.
Semiconductor Qubits and Quantum Dots: These possess long coherent times.
Have Quantum Computers Been Built?
Quantum
computers with a few qubits (up to 10) have been built in research labs
and they do perform some basic mathematical computations. One of the
most inventive companies of the world, IBM is investing in quantum
computing research because they foresee great market potential. Many
other companies as also computer scientists believe that once quantum
computers leap forth from research labs into commercial territory, they
could become game changers. A fully functional quantum device with
thousands of entangled qubits is still a futuristic idea. However,
there's much less speculation in the capabilities of quantum computers.
In fact, many scientists agree that an actual full-scale powerful device
could well open up possibilities that have not been imagined or
perceived with the current toy models, simulation algorithms and
theories.
Is it Already in the Commercial Market?
If you
thought the world of quantum computing is bizarre enough, here's
something that's on the same lines. In May 2011, a Canadian company
called D-wave Systems was in the news for having sold a 128-qubit
quantum computing system, called "D-Wave One", to a global security
company, Lockheed Martin. While some researchers have questioned the
company's claims of having built a mythical system known to exist only
theoretically, however, the company is moving ahead with building even
more powerful quantum computers by scaling up to thousands of qubits.
Lockheed Martin being a security company, all design aspects and
applications of its state-of-the-art purchase have been kept a secret,
further fueling speculation.
Uses of Quantum Computers
Quantum
computers were always thought of in the context of complex mathematical
computations and aspects such as machine learning and artificial
intelligence. Quantum computing promises to have the capacity to
simultaneously compare a huge number of variables and working out a huge
number of probabilities. These attributes make it ideal for application
in the following area.
Medical Diagnosis: In this case,
several symptoms will need to be compared with several disease
characteristics and the results of several other diagnostic tests.
Bioinformatics/Biomedical Simulations: The parallel processing power
of quantum computers will be helpful in comparing huge clinical data
sets with statistical and probabilistic tools.
Robotics: Machine
learning and artificial intelligence concepts can utilize the power of
quantum computers to power the brains of intelligent robots.
Climate Modeling: Again due to the capacity to perform parallel
processing of a range of variables, quantum computers can provide
hi-tech simulations.
Cryptanalysis: Circumventing security
encryption by cracking ciphers to expose weaknesses in the security
systems, this technique involves working with various combination of
secure keys which is a trademark use for quantum computers.
While
quantum computing is perhaps not going to dramatically alter our daily
use of computers except to the extent of miniaturization of processing
hardware, its application in the above fields will be something to look
forward to. One can only imagine how baffling the impact of such a
quantum leap in technology can be.
By Preeti Sunil
