Leaps in Quantum Computing
Leaps in Quantum Computing
Apr 2000
On December 29th 1959 Richard Feynman gave a visionary talk entitled "There's Plenty of Room at the Bottom"outlining the possibilities allowed by conventional laws of physics for a new type of computers.
"You realize, of course, that if we had a operational quantum computer today, nothing on the Internet would be safe.
Our current methods of encrypting secret or personal data, like the RSA public key encryption algorithm currently usedin web browsers,
would be nearly worthless."Raymond Laflamme
NMR Quantum Computing Researcher  
For decades advances in conventional computer technology have been following
Moore'sLaw
of doubling power every 18 months. However, to
rescue Moore's Law in
the nextcouple of decades will take some big advances  among other things we are soon
going to be entangled in quantum mechanics rather than conventional electronics. However,
quantum mechanics is also the key to a brand new technology with much higher capability.
May 4, 1998
after decades of theoretical physics, a 2 qubit quantum computer capable of loading
data and reading out a result is announced. Modern digital computers are based on
bits  something which can be toggled back and forthbetween two states (e.g.
magnetized or demagnetized). By representing these two states as 0 and 1, we can do
binary arithmetic with sets of bits and the devices that toggle them. Everything else
is built from there ... In quantum mechanics we see many physical systems as have two
states (e.g. spin up or spin down). We refer to each such "bit" as a
qubit. However, qubits are quantum mechanical and as such they behave much
differently than bits. They exist in a superposition of 0 and 1 states simultaneously
and may couple with neighboring qubits.
There is an old saying that "when all you have is a hammer, everything looks
like a nail". To somebody trained in conventional computing a qubit might look
completely impractical because they have learned to see problems in terms of how you
can solve them with bits and bit operations. However, as we examine what can be done
with qubits, there are many problems where they are clearly the superior tool to use.
An array of qubits operates as a parallel computer capable of performing a large
calculation in one step, and the power grows rapidly with the number of qubits. One
application is the factoring of numbers. This is significant because it is the basis
of standard security schemes for encrypting numbers.A 30 qubit computer would be 5 times
more powerful than the worlds fastest present supercomputer and could break any known code.
In the last couple of weeks there have been big announcements from rivals in the
size of operating quantum computers. Mar. 16 scientists at the
NIST (National Institute for Standards and Technology)
announced the "quantum
entanglement of four particles"  published in Nature.
One week later scientistsat LANL (Los Alamos National
Laboratory) announced a seven
bit NMR quantum computer. NIST physicist David Wineland predicts that while NMR has a headstart,
it will hit a fundamentalblock at 15 qubits beyond which the interaction between the particles will
start to disappear. That is why they are pursuing the trapped ion approach instead.
The future development of quantum computing is impossible to predict. Scientists in the
field say useful computers could be a few years away, or they could be decades away. The
history is too short to say whether Moore's Law is being followed or not, but 18 months ago
the first 2qubit computer was shortly followed by a 3qubit computer and now a 4qubit
announcement was shortly followed by 7qubit announcement. So far, doubling every 18 months
looks pretty accurate. IF this rate should continue, we'll see that 30 qubit
computer in three or four years. Further Reading on Quantum Computing
Frequently Asked Questions about Quantum Computation
From the Centre for Quantum Computation  part of the University of Oxford.
Quantum Computing with Molecules
Scientific American article by Neil Gershenfeld and Isaac L. Chuang  developers of the first 2 qubit computer.
Quantum Computer Development
A review of the status, logic and prospects of quantum computing.
Quantum Leap in Computing
Mar 23, 2000 announcement of a 7 qubit computer
Quantum Logic
For those who know what a wavefunction is: how to implement AND/OR/NOT etc with qubits.
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