# The Practicality of Quantum Computers Presentation notes

Document Sample

```					The Practicality of Quantum Computers Presentation

I.      Introduction
a. Quantum computers have the potential to be the next evolution of computers;
however, current technology cannot produce efficient quantum computers.
b. First define a classical
i. Classical computers are those that function based on the principles of classical
physics
ii. For the most part, all computers today are classical computers
iii. Bits; they have values of either zero or one which correspond to values like yes
and no
1. They are represented by electrical charges
2. Pass through logical “tests” in order to arrive at a desired answer
3. A computers processing power increases with the ability to pass more
bits more quickly though the computer
c. Now define what is a quantum computer
i. They are computers that exploit specific phenomena of quantum mechanics like
superposition and entanglement.
ii. The bits of a quantum computer are known as qubits (quantum bits)
1. This bits are composed of a particle which has a specific state, and this is
a quantum mechanical principle
2. Quantum mechanics allows for these bits to be put into a superposition
a. The value of a qubit can now be 0 or 1, or a combination of the
two
i. Half spin up and half spin down
3. Superposition allows quantum computers to carry out calculations on
their quits simultaneously
II.     Early Calculations and Promises – Lov Grover’s Paper
a. Say that one wants to search for an entry in a phonebook containing one million entries,
and the only thing that you know about the certain entry is the address. With a classical
computer one would have to search the database one-by-one. The worst case scenario
would have to be searching the phonebook 999,999 times; so on average the computer
would have to make 500,000 calculations. With a quantum computer, this can be sped
up to a more reasonable amount of time. First, each entry would be stored in a
quantum computer’s memory as a quantum state. Each qubit has 2q states where q is
the number of qubits, so this situation would require approximately twenty qubits (220
= 1,048,576 states). Once inside the computer’s memory, one would have to place a
qubit into a superposition of the states above, and apply a certain algorithm or
calculation. Superposition allows for these calculations to be carried out on each of the
states simultaneously. This process reduces the average number of calculations from
500,000 to just 1,000
i. The author of this study then goes on to say that when it comes to creating a
quantum computer, once technology catches up with these scenarios, the last
thing to do would be to create the necessary algorithms
b. With quantum computer’s calculation abilities, very effecting keys can be produces to
encrypt data, also, codes that have never been cracked before like those that I
mentioned during my 2 min talk
III.    Practicality
a. Quantum computers are great for crunching though large amounts of data, but when it
comes to many of the tasks and you and I perform everyday like accessing are large
music and picture libraries, quantum computers don’t seem like the best candidate
b. “In case anyone is starting to look forward to the bright future of compact and handy
quantum hard drives with the storage capacity of a trillion Libraries of Congresses, it is
important to realize that almost none of the information in such a device would be
accessible. Even though our 100 quantum coins in principle contain a stupendous
amount of information, trying to read it would force each coin into a definite state of
either heads or tails, yielding only 100 bits of information”
i. Another side affect of measuring the final state of a qubit is that doing so forces
it into a certain position like either an up or down spin. This makes quantum
hard drives completely useless without some sort of technological
ii. Remember that it takes eight classical bits just to represent a letter, so our now
100 classical bits of the Library of Congress is now useless.
iii. With Lov Grover’s scenario, the trick would be to get all of the information from
the phonebook search out of the memory.
1. Lov Grove himself devised a quantum computer algorithm that search
an unsorted list for a certain element quadratically faster rather than
exponentially on a quantum computer. In his paper, he then applied
this algorithm to his phonebook situation. It increased the chance that
when one measures the system, it will collapse onto the state that the
search was intended.
c. Another issue is decoherance
i. “To remain in an intermediate, superposed state, a quantum-mechanical system
needs to be almost totally isolated from its environment; the slightest
interaction with anything outside itself will perturb the system, destroy the
superposition and upset the computation. As a result, anyone who wants to
build a quantum computer must be careful to shield it from heat, cosmic rays
and other potential outside influences-including outside observers,” or as
physicists would say, it de-coheres
d. All computers are prone to errors too, but fortuantly, quantum error correction is
possible with an algorithm designed by Peter Shor in 1995 that was highlighted in Lov
Grover’s paper
i. In 1995 the mathematician Peter W. Shor… and the physicist Andrew M.
Steane…independently devised a scheme that deftly tiptoes through the
quantum minefield. The scheme detects error in a way that reveals nothing
about the ongoing computation (and thus does not ruin the superposition).
Then it fixes the error by means of another quantum computation, which also
keeps the quantum system intact”
e. Also when considering the practicality of quantum computers, scalability is a major
concern.
i. Most of the scenarios that I talked about function only on paper because the
necessary equipment to test them on hasn’t been developed.
ii. D-Wave, a quantum computing company from Canada, demonstrated its
quantum computer named Orion. Their quantum computer uses niobium
atoms as qubits because scientists understand how magnetic fields interact with
this atom. The company also stated that it plans to introduce system that
operate with thirty-two qubits by the end of 2007, 512 qubits by Q2 of 2008,
and 1,024 by the end of that year.
1. These systems are not ready for mass adoption though because their
operating requirements, like a temperature around absolute zero, are
not practical
f. Qubits are also very difficult to transport around a quantum computer, luckily many
improvements are being made in this field.
i. Fortunately, modern materials are being developed to transport qubits using
superconducting wiring
ii. Also the field of quantum teleportation is currently being researching as a wiring
alternative
1. Entanglement, the principle behind quantum teleportation, is when two
2. .The effects of entanglement are similar to those of Einstein’s “spooky
action at a distance” observation
3. Draw on board using particles a
4. Mention the classical transmission that is necessary to achieve a
successful teleportation, and successful teleportation had occurred with
laser beams across large distances.
iii. Quantum teleportation also allows for data privacy because the only thing that
an outsider can understand from the classical transmission are the
measurements, and they don’t have the entangled particle which is necessary.
iv. Quantum teleportation can also be implemented to create networks of
quantum computers which is truly amazing, supercomputers will become
obsolete
IV.   Conclusion
a. Many computer scientists feel that quantum computers are the next stage of
supercomputing with their undeniable power. However, this technology is still in its
infancy. Just like the first classical computers, technological advancement is necessary
for their adoption. Many remember when computers like the UNIVAC occupied rooms
and could only carry out basic calculations, and now they advancing into the
microscopic world. Many companies like D-Wave are making vast improvements in this
field, and they are also readying their quantum computers for commercial use. The
benefits of quantum computers are too great to ignore. As technology catches up with
theory, the computing world will most likely behold its evolution.

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 7 posted: 12/10/2011 language: pages: 3