Sweet huh?

A relative of the crocodile family, this 12 foot long monster would have been eating surfers in the south-eastern Pacific about 135 million years ago. I'd love to have one of those around.





It'd be an awesome pet. I'd name him Timmy and feed him people that were mean to me in school.


JMG

Natalie Holloway blah blah blah. You all know the story. Now her mom and the FRICKIN Governor of Alabama are pushing for a boycott of Aruba. First of all, there's only like 19 people who are from Alabama who could even AFFORD to visit Aruba. Come on.

"OOoooooooo a bunch of rednecks aren't going to visit our country anymore. We're gonna hire Army Rangers to come and conduct the investigation now."

I call bullshit on that.

And anyway, is a boycott gonna make the chick become not-shark chum? Damn no.


JMG

Traumaie Silkfen had a red glass clearcrystal eye that glowed with anger and excitement. It had been a hypothetical heretofore, in those castlemoss grey days and only now was it slow developing into a fetal bloodmass of something.

Stilvane the Redactor found many ways in his groundfertile mind to express in the proper terms and forms, his distaste for this ill thing. Such problems were not unheard of, simply rare. Rarer still was the low growl-howl sound from Traumaie Silkfen that was his means communication. If one were to imagine the sound of a tree taking path past another at a very short distance such that their two trunks were to scrape and groan violently, then add into this the sound of a fieldswolf mourning for a torn-apart mate, one would somewhat have a trifle of a notion of the speech of Traumaie Silkfen. This sound echoed forth summoning Stilvane the Redactor from his private worksroom.

The room of The Redactor was little more than a closet compared to the confliction room in which Silkfen waited. But even having said that, its area was no real pittance. Upon entering the worksroom, one’s eyes would most probably attach themselves to the massive fireplace at the far end of the room. It was not so much a fire place, it seemed, as a huge gothic cathedral built to honor flame and smoke. And perhaps it was, in a way. Along the easternmost wall there were shelves and shelves packed with papers and books. Some lost to dust and age and earwigs.


This is tentatively titled, "The Walking Time". Anyone have any ideas where I should go with this?

Whitewash


Waiting for winter|or water
Any change of scenery|any change of pace
Or humidity;
Do you recall the snowfall?

Or being buried in the
difference?

Never so cold as when you’re alone
Forgot
Forget
Forget
Indecency|indifference
So
Somnambu
l
e
n
t

and comfortable
.

Waiting for winter:
Do you recall the snowfall?
Drowning in this subtle sameness
Never so tired as when you’re asleep.

lance d with the key to an f 23
tearin towels of some heads with the usmc
baddest muther fuckers in the us of a
we woulda won this fuckin war if skinny d led the way

He said we nuke the camel fuckers on the first day
not a goddamn dead body, not american's anyway
what's a terrorist but a corpse that's running late
Ole D said here's your damn funeral, now face the east and pray

Word to your mother

I can’t win it I’m in
it can I finish this sentence the
big ending’s intriguing
I know you know I’m winging
this phrenetic phrasing
the crazy phoenetics hectic
I wrecked it
any chance of seeing this girl naked
I’ve netted zero
my heros
vetted this shit
truly better at this
but that ain’t hard is it
this minute
I’m rotting slolwy
my dna unrolling unraveling
becoming unstable damaged
they call it aging I call it panic
this isnt natural
these caustic chemicals
decaying my genes making me old beyond dreams
and the dying ribosomes or something causing pain
down in my sacroiliac
, fo buisiness majors that would be my lower back,
chromosomal decay I need a soma ok
, or some oxycodone to brace
my brain for this low back bone pain

There are 2 things that really piss me off regarding all this Bush hatred going on. The first thing, obviously, is listening to all these idiots, mostly on the left, whose only goal in life is to hate the President and do something to damage him or the administration. They don't want to push an agenda or an ideology. They don't want to win elections. Hey, DNC, if you actually DO want to win elections, quit listening to these morons, get some ideas, and try to run a decent campaign one day.

The second thing that pisses me off with this is all these idiots on the right who act like no one has ever said so many bad things about any other President, that no other President has been as hated, so reviled, as Bush II. Have they all forgotten 1992-2000? These dolts hated President Clinton at least as much as these other dolts hate President Bush now. Instead of admitting that, we get folks like Hannity complaining and whining about people saying bad things about Bush that hurt his feelings.

Come on people, remember reality? Remember? I know it hurts, but at least try not to lie ALL the time.

AV

America may have some problems, but it’s our home. It’s our team. And if you don’t want to root for your team, you should get the hell out of the stadium.

Go America.

Go Broncos.

This is lifted from an article by William Rivers Pitt at InformationClearingHouse.comStrategy, Forces and Resources for a New Century."

This would be a damn funny conspiracy theory, except for the fact that it's all true. So it's just damn scary. Here's the real website for PNAC. I encourage you to check it out yourself.



The Project for the New American Century.

William Rivers Pitt: 02/25/03

The Project for the New American Century, or PNAC, is a Washington-based
think tank created in 1997. Above all else, PNAC desires and demands one
thing: The establishment of a global American empire to bend the will of
all nations. They chafe at the idea that the United States, the last
remaining superpower, does not do more by way of economic and military
force to bring the rest of the world under the umbrella of a new
socio-economic Pax Americana.

The fundamental essence of PNAC's ideology can be found in a White Paper
produced in September of 2000 entitled "Rebuilding America's Defenses:
Strategy, Forces and Resources for a New Century." In it, PNAC outlines
what is required of America to create the global empire they envision.
According to PNAC, America must:
* Reposition permanently based forces to Southern Europe, Southeast Asia
and the Middle East;
* Modernize U.S. forces, including enhancing our fighter aircraft,
submarine and surface fleet capabilities;
* Develop and deploy a global missile defense system, and develop a
strategic dominance of space;
* Control the "International Commons" of cyberspace;
* Increase defense spending to a minimum of 3.8 percent of gross domestic
product, up from the 3 percent currently spent.


Most ominously, this PNAC document described four "Core Missions" for the
American military. The two central requirements are for American forces to
"fight and decisively win multiple, simultaneous major theater wars," and
to "perform the 'constabulary' duties associated with shaping the security
environment in critical regions." Note well that PNAC does not want America
to be prepared to fight simultaneous major wars. That is old school. In
order to bring this plan to fruition, the military must fight these wars
one way or the other to establish American dominance for all to see.

Why is this important? After all, wacky think tanks are a cottage industry
in Washington, DC. They are a dime a dozen. In what way does PNAC stand
above the other groups that would set American foreign policy if they could?
Two events brought PNAC into the mainstream of American government: the
disputed election of George W. Bush, and the attacks of September 11th.
When Bush assumed the Presidency, the men who created and nurtured the
imperial dreams of PNAC became the men who run the Pentagon, the Defense
Department and the White House. When the Towers came down, these men saw,
at long last, their chance to turn their White Papers into substantive
policy.

Vice President Dick Cheney is a founding member of PNAC, along with Defense
Secretary Donald Rumsfeld and Defense Policy Board chairman Richard Perle.
Deputy Defense Secretary Paul Wolfowitz is the ideological father of the
group. Bruce Jackson, a PNAC director, served as a Pentagon official for
Ronald Reagan before leaving government service to take a leading position
with the weapons manufacturer Lockheed Martin.


PNAC is staffed by men who previously served with groups like Friends of
the Democratic Center in Central America, which supported America's bloody
gamesmanship in Nicaragua and El Salvador, and with groups like The
Committee for the Present Danger, which spent years advocating that a
nuclear war with the Soviet Union was "winnable."


PNAC has recently given birth to a new group, The Committee for the
Liberation of Iraq, which met with National Security Advisor Condoleezza
Rice in order to formulate a plan to "educate" the American populace about
the need for war in Iraq. CLI has funneled millions of taxpayer dollars to
support the Iraqi National Congress and the Iraqi heir presumptive, Ahmed
Chalabi. Chalabi was sentenced in absentia by a Jordanian court in 1992 to
22 years in prison for bank fraud after the collapse of Petra Bank, which
he founded in 1977. Chalabi has not set foot in Iraq since 1956, but his
Enron-like business credentials apparently make him a good match for the
Bush administration's plans.


PNAC's "Rebuilding America's Defenses" report is the institutionalization
of plans and ideologies that have been formulated for decades by the men
currently running American government. The PNAC Statement of Principles is
signed by Cheney, Wolfowitz and Rumsfeld, as well as by Eliot Abrams, Jeb
Bush, Bush's special envoy to Afghanistan Zalmay Khalilzad, and many
others. William Kristol, famed conservative writer for the Weekly Standard,
is also a co-founder of the group. The Weekly Standard is owned by Ruppert
Murdoch, who also owns international media giant Fox News.


The desire for these freshly empowered PNAC men to extend American hegemony
by force of arms across the globe has been there since day one of the Bush
administration, and is in no small part a central reason for the Florida
electoral battle in 2000. Note that while many have said that Gore and Bush
are ideologically identical, Mr. Gore had no ties whatsoever to the fellows
at PNAC. George W. Bush had to win that election by any means necessary,
and PNAC signatory Jeb Bush was in the perfect position to ensure the rise
to prominence of his fellow imperialists. Desire for such action, however,
is by no means translatable into workable policy. Americans enjoy their
comforts, but don't cotton to the idea of being some sort of Neo-Rome.

On September 11th, the fellows from PNAC saw a door of opportunity open
wide before them, and stormed right through it.


Bush released on September 20th 2001 the "National Security Strategy of the
United States of America." It is an ideological match to PNAC's "Rebuilding
America's Defenses" report issued a year earlier. In many places, it uses
exactly the same language to describe America's new place in the world.

Recall that PNAC demanded an increase in defense spending to at least 3.8%
of GDP. Bush's proposed budget for next year asks for $379 billion in
defense spending, almost exactly 3.8% of GDP.


In August of 2002, Defense Policy Board chairman and PNAC member Richard
Perle heard a policy briefing from a think tank associated with the Rand
Corporation. According to the Washington Post and The Nation, the final
slide of this presentation described "Iraq as the tactical pivot, Saudi
Arabia as the strategic pivot, and Egypt as the prize" in a war that would
purportedly be about ridding the world of Saddam Hussein's weapons. Bush
has deployed massive forces into the Mideast region, while simultaneously
engaging American forces in the Philippines and playing nuclear chicken
with North Korea. Somewhere in all this lurks at least one of the "major
theater wars" desired by the September 2000 PNAC report.


Iraq is but the beginning, a pretense for a wider conflict. Donald Kagan, a
central member of PNAC, sees America establishing permanent military bases
in Iraq after the war. This is purportedly a measure to defend the peace in
the Middle East, and to make sure the oil flows. The nations in that
region, however, will see this for what it is: a jump-off point for
American forces to invade any nation in that region they choose to. The
American people, anxiously awaiting some sort of exit plan after America
defeats Iraq, will see too late that no exit is planned.


All of the horses are traveling together at speed here. The defense
contractors who sup on American tax revenue will be handsomely paid for
arming this new American empire. The corporations that own the news media
will sell this eternal war at a profit, as viewership goes through the
stratosphere when there is combat to be shown. Those within the
administration who believe that the defense of Israel is contingent upon
laying waste to every possible aggressor in the region will have their
dreams fulfilled. The PNAC men who wish for a global Pax Americana at
gunpoint will see their plans unfold. Through it all, the bankrollers from
the WTO and the IMF will be able to dictate financial terms to the entire
planet. This last aspect of the plan is pivotal, and is best described in
the newly revised version of Greg Palast's masterpiece, "The Best Democracy
Money Can Buy."


There will be adverse side effects. The siege mentality average Americans
are suffering as they smother behind yards of plastic sheeting and duct
tape will increase by orders of magnitude as our aggressions bring forth
new terrorist attacks against the homeland. These attacks will require the
implementation of the newly drafted Patriot Act II, an augmentation of the
previous Act that has profoundly sharper teeth. The sun will set on the
Constitution and Bill of Rights.

The American economy will be ravaged by the need for increased defense
spending, and by the aforementioned "constabulary" duties in Iraq,
Afghanistan and elsewhere. Former allies will turn on us. Germany, France
and the other nations resisting this Iraq war are fully aware of this game
plan. They are not acting out of cowardice or because they love Saddam
Hussein, but because they mean to resist this rising American empire, lest
they face economic and military serfdom at the hands of George W. Bush.
Richard Perle has already stated that France is no longer an American ally.

As the eagle spreads its wings, our rhetoric and their resistance will
become more agitated and dangerous.


Many people, of course, will die. They will die from war and from want,
from famine and disease. At home, the social fabric will be torn in ways
that make the Reagan nightmares of crack addiction, homelessness and AIDS
seem tame by comparison.


This is the price to be paid for empire, and the men of PNAC who now
control the fate and future of America are more than willing to pay it. For
them, the benefits far outweigh the liabilities.


The plan was running smoothly until those two icebergs collided. Millions
and millions of ordinary people are making it very difficult for Bush's
international allies to keep to the script. PNAC may have designs for the
control of the "International Commons" of the Internet, but for now it is
the staging ground for a movement that would see empire take a back seat to
a wise peace, human rights, equal protection under the law, and the
preponderance of a justice that will, if properly applied, do away forever
with the anger and hatred that gives birth to terrorism in the first place.
Tommaso Palladini of Milan perhaps said it best as he marched with his
countrymen in Rome. "You fight terrorism," he said, "by creating more
justice in the world."


The People versus the Powerful is the oldest story in human history. At no
point in history have the Powerful wielded so much control. At no point in
history has the active and informed involvement of the People, all of them,
been more absolutely required. The tide can be stopped, and the men who
desire empire by the sword can be thwarted. It has already begun, but it
must not cease. These are men of will, and they do not intend to fail.

William Rivers Pitt is a New York Times bestselling author of two books -
"War On Iraq" (with Scott Ritter) available now from Context Books, and
"The Greatest Sedition is Silence," available in May 2003 from Pluto Press.
He teaches high school in Boston, MA.
Scott Lowery contributed research to this report.

I lifted this from some site. Read it, and know all.


What is quantum computation?
A fundamentally new mode of information processing that can be performed only by harnessing physical phenomena unique to quantum mechanics (especially quantum interference).

What is quantum mechanics?

The deepest theory of physics; the framework within which all other current theories, except the general theory of relativity, are formulated. Some of its features are:

Quantisation (which means that observable quantities do not vary continuously but come in discrete chunks or 'quanta'). This is the one that makes computation, classical or quantum, possible at all.

Interference (which means that the outcome of a quantum process in general depends on all the possible histories of that process). This is the one that makes quantum computers qualitatively more powerful than classical ones.

Entanglement (Two spatially separated and non-interacting quantum systems that have interacted in the past may still have some locally inaccessible information in common - information which cannot be accessed in any experiment performed on either of them alone.) This is the one that makes quantum cryptography possible.

What's all this about parallel universes?

If you only want to predict what quantum computers will be able to do, you only need the equations of quantum mechanics. But if you want to explain how they will do it, you need to understand that the computer you can see and touch is only one tiny facet of a far larger object, which is just as real even though its existence is only detectable indirectly, through the computational work it does for us. The best way to describe the structure of a quantum computer is not at present clear, but in some respects it is like many computers similar to the one we see, performing different but correlated computations which affect each other through quantum interference.

In quantum computers, the effects of quantum interference are writ large. But the theory says that the whole of reality behaves in the same way. So the whole universe that we see around us is full of a subtle inner structure. This all-pervasive property is felt by some physicists to be best described as a multiverse, which contains many universes like ours, interacting only through quantum interference.

What will quantum computers be good at?

These are the most important applications currently known:
Cryptography: perfectly secure communication.
Searching, especially algorithmic searching (Grover's algorithm).
Factorising large numbers very rapidly (Shor's algorithm).
Simulating quantum-mechanical systems efficiently.
At which institutions can I study quantum computing?

Where can I find out more about quantum computation and related matters?
Start at our Home Page or at our Introduction and Tutorials page.

Minds, Machines and the Multiverse: The Quest for the Quantum Computer by Julian Brown. Simon and Schuster 2000.A good non-technical overview of the current state of the field and its meteoric history. The whole of chapter one is freely available online from here.

Quantum Computing by Josef Gruska. McGraw Hill 1999.A good technical introduction to the field.

See also The Fabric of Reality by David Deutsch.

For more detailed/technical information you can look at our literature list.
Last modified by David Deutsch17 March 2001

Civilisation has advanced as people discovered new ways of exploiting various physical resources such as materials, forces and energies. In the twentieth century information was added to the list when the invention of computers allowed complex information processing to be performed outside human brains. The history of computer technology has involved a sequence of changes from one type of physical realisation to another --- from gears to relays to valves to transistors to integrated circuits and so on. Today's advanced lithographic techniques can squeeze fraction of micron wide logic gates and wires onto the surface of silicon chips. Soon they will yield even smaller parts and inevitably reach a point where logic gates are so small that they are made out of only a handful of atoms. On the atomic scale matter obeys the rules of quantum mechanics, which are quite different from the classical rules that determine the properties of conventional logic gates. So if computers are to become smaller in the future, new, quantum technology must replace or supplement what we have now. The point is, however, that quantum technology can offer much more than cramming more and more bits to silicon and multiplying the clock-speed of microprocessors. It can support entirely new kind of computation with qualitatively new algorithms based on quantum principles!

To explain what makes quantum computers so different from their classical counterparts we begin by having a closer look at a basic chunk of information namely one bit. From a physical point of view a bit is a physical system which can be prepared in one of the two different states representing two logical values --- no or yes, false or true, or simply 0 or

1. For example, in digital computers, the voltage between the plates in a capacitor represents a bit of information: a charged capacitor denotes bit value 1 and an uncharged capacitor bit value 0. One bit of information can be also encoded using two different polarisations of light or two different electronic states of an atom. However, if we choose an atom as a physical bit then quantum mechanics tells us that apart from the two distinct electronic states the atom can be also prepared in a coherent superposition of the two states. This means that the atom is both in state 0 and state 1.

To get used to the idea that a quantum object can be in `two states at once' it is helpful to consider the following experiment (Fig.A and B) Let us try to reflect a single photon off a half-silvered mirror i.e. a mirror which reflects exactly half of the light which impinges upon it, while the remaining half is transmitted directly through it (Fig. A). Where do you think the photon is after its encounter with the mirror --- is it in the reflected or in the transmitted beam? It seems that it would be sensible to say that the photon is either in the transmitted or in the reflected beam with the same probability. That is one might expect the photon to take one of the two paths choosing randomly which way to go.

Indeed, if we place two photodetectors behind the half-silvered mirror in direct lines of the two beams, the photon will be registered with the same probability either in the detector 1 or in the detector 2. Does it really mean that after the half-silvered mirror the photon travels in either reflected or transmitted beam with the same probability 50%? No, it does not ! In fact the photon takes `two paths at once'. This can be demonstrated by recombining the two beams with the help of two fully silvered mirrors and placing another half-silvered mirror at their meeting point, with two photodectors in direct lines of the two beams (Fig. B). With this set up we can observe a truly amazing quantum interference phenomenon.


If it were merely the case that there were a 50% chance that the photon followed one path and a 50% chance that it followed the other, then we should find a 50% probability that one of the detectors registers the photon and a 50% probability that the other one does. However, that is not what happens. If the two possible paths are exactly equal in length, then it turns out that there is a 100% probability that the photon reaches the detector 1 and 0% probability that it reaches the other detector 2. Thus the photon is certain to strike the detector 1! It seems inescapable that the photon must, in some sense, have actually travelled both routes at once for if an absorbing screen is placed in the way of either of the two routes, then it becomes equally probable that detector 1 or 2 is reached (Fig. 1c). Blocking off one of the paths actually allows detector 2 to be reached; with both routes open, the photon somehow knows that it is not permitted to reach detector2, so it must have actually felt out both routes. It is therefore perfectly legitimate to say that between the two half-silvered mirrors the photon took both the transmitted and the reflected paths or, using more technical language, we can say that the photon is in a coherent superposition of being in the transmitted beam and in the reflected beam. By the same token an atom can be prepared in a superposition of two different electronic states, and in general a quantum two state system, called a quantum bit or a qubit, can be prepared in a superposition of its two logical states 0 and 1. Thus one qubit can encode at a given moment of time both 0 and 1.

Now we push the idea of superposition of numbers a bit further. Consider a register composed of three physical bits. Any classical register of that type can store in a given moment of time only one out of eight different numbers i.e the register can be in only one out of eight possible configurations such as 000, 001, 010, ... 111. A quantum register composed of three qubits can store in a given moment of time all eight numbers in a quantum superposition (Fig. 2). This is quite remarkable that all eight numbers are physically present in the register but it should be no more surprising than a qubit being both in state 0 and 1 at the same time. If we keep adding qubits to the register we increase its storage capacity exponentially i.e. three qubits can store 8 different numbers at once, four qubits can store 16 different numbers at once, and so on; in general L qubits can store 2L numbers at once. Once the register is prepared in a superposition of different numbers we can perform operations on all of them. For example, if qubits are atoms then suitably tuned laser pulses affect atomic electronic states and evolve initial superpositions of encoded numbers into different superpositions. During such evolution each number in the superposition is affected and as the result we generate a massive parallel computation albeit in one piece of quantum hardware. This means that a quantum computer can in only one computational step perform the same mathematical operation on 2L different input numbers encoded in coherent superpositions of L qubits. In order to acomplish the same task any classical computer has to repeat the same computation 2L times or one has to use 2L different processors working in parallel. In other words a quantum computer offers an enormous gain in the use of computational resources such as time and memory.

But this, after all, sounds as yet another purely technological progress. It looks like classical computers can do the same computations as quantum computers but simply need more time or more memory. The catch is that classical computers need exponentially more time or memory to match the power of quantum computers and this is really asking for too much because an exponential increase is really fast and we run out of available time or memory very quickly. Let us have a closer look at this issue.

In order to solve a particular problem computers follow a precise set of instructions that can be mechanically applied to yield the solution to any given instance of the problem. A specification of this set of instructions is called an algorithm. Examples of algorithms are the procedures taught in elementary schools for adding and multiplying whole numbers; when these procedures are mechanically applied, they always yield the correct result for any pair of whole numbers. Some algorithms are fast (e.g. multiplication) other are very slow (e.g. factorisation, playing chess). Consider, for example, the following factorisation problem

? x ? = 29083

How long would it take you, using paper and pencil, to find the two whole numbers which should be written into the two boxes (the solution is unique)? Probably about one hour. Solving the reverse problem
127 x 129 = ? ,

again using paper and pencil technique, takes less than a minute. All because we know fast algorithms for multiplication but we do not know equally fast ones for factorisation. What really counts for a ``fast'' or a ``usable'' algorithm, according to the standard definition, is not the actual time taken to multiply a particular pairs of number but the fact that the time does not increase too sharply when we apply the same method to ever larger numbers. The same standard text-book method of multiplication requires little extra work when we switch from two three digit numbers to two thirty digits numbers. By contrast, factoring a thirty digit number using the simplest trial divison method (see inset 1) is about 1013 times more time or memory consuming than factoring a three digit number. The use of computational resources is enormous when we keep increasing the number of digits. The largest number that has been factorised as a mathematical challenge, i.e. a number whose factors were secretly chosen by mathematicians in order to present a challenge to other mathematicians, had 129 digits. No one can even conceive of how one might factorise say thousand-digit numbers; the computation would take much more that the estimated age of the universe.
Skipping details of the computational complexity we only mention that computer scientists have a rigorous way of defining what makes an algorithm fast (and usable) or slow (and unusable). For an algorithm to be fast, the time it takes to execute the algorithm must increase no faster than a polynomial function of the size of the input. Informally think about the input size as the total number of bits needed to specify the input to the problem, for example, the number of bits needed to encode the number we want to factorise. If the best algorithm we know for a particular problem has the execution time (viewed as a function of the size of the input) bounded by a polynomial then we say that the problem belongs to class P. Problems outside class P are known as hard problems.

Thus we say, for example, that multiplication is in P whereas factorisation is not in P and that is why it is a hard problem. Hard does not mean ``impossible to solve'' or ``non-computable'' --- factorisation is perfectly computable using a classical computer, however, the physical resources needed to factor a large number are such that for all practical purposes, it can be regarded as intractable (see inset 1).


It worth pointing out that computer scientists have carefully constructed the definitions of efficient and inefficient algorithms trying to avoid any reference to a physical hardware. According to the above definition factorisation is a hard problem for any classical computer regardless its make and the clock-speed. Have a look at Fig.3 and compare a modern computer with its ancestor of the nineteenth century, the Babbage differential engine. The technological gap is obvious and yet the Babbage engine can perform the same computations as the modern digital computer. Moreover, factoring is equally difficult both for the Babbage engine and top-of-the-line connection machine; the execution time grows exponentially with the size of the number in both cases. Thus purely technological progress can only increase the computational speed by a fixed multiplicative factor which does not help to change the exponential dependance between the size of the input and the execution time. Such change requires inventing new, better algorithms. Although quantum computation requires new quantum technology its real power lies in new quantum algorithms which allow to exploit quantum superposition that can contain an exponential number of different terms. Quantum computers can be programed in a qualitatively new way. For example, a quantum program can incorporate instructions such as `... and now take a superposition of all numbers from the previous operations...'; this instruction is meaningless for any classical data processing device but makes lots of sense to a quantum computer. As the result we can construct new algorithms for solving problems, some of which can turn difficult mathematical problems, such as factorisation, into easy ones!

The story of quantum computation started as early as 1982, when the physicist Richard Feynman considered simulation of quantum-mechanical objects by other quantum systems[1]. However, the unusual power of quantum computation was not really anticipated untill the 1985 when David Deutsch of the University of Oxford published a crucial theoretical paper[2] in which he described a universal quantum computer. After the Deutsch paper, the hunt was on for something interesting for quantum computers to do. At the time all that could be found were a few rather contrived mathematical problems and the whole issue of quantum computation seemed little more than an academic curiosity. It all changed rather suddenly in 1994 when Peter Shor from AT&T's Bell Laboratories in New Jersey devised the first quantum algorithm that, in principle, can perform efficient factorisation[3].This became a `killer application' --- something very useful that only a quantum computer could do. Difficulty of factorisation underpins security of many common methods of encryption; for example, RSA --- the most popular public key cryptosystem which is often used to protect electronic bank accounts gets its security from the difficulty of factoring large numbers. Potential use of quantum computation for code-breaking purposes has raised an obvious question --- what about building a quantum computer.

In principle we know how to build a quantum computer; we can start with simple quantum logic gates and try to integrate them together into quantum circuits. A quantum logic gate, like a classical gate, is a very simple computing device that performs one elementary quantum operation, usually on two qubits, in a given period of time[4]. Of course, quantum logic gates are different from their classical counterparts because they can create and perform operations on quantum superpositions (cf. inset 2). However if we keep on putting quantum gates together into circuits we will quickly run into some serious practical problems. The more interacting qubits are involved the harder it tends to be to engineer the interaction that would display the quantum interference. Apart from the technical difficulties of working at single-atom and single-photon scales, one of the most important problems is that of preventing the surrounding environment from being affected by the interactions that generate quantum superpositions. The more components the more likely it is that quantum computation will spread outside the computational unit and will irreversibly dissipate useful information to the environment. This process is called decoherence. Thus the race is to engineer sub-microscopic systems in which qubits interact only with themselves but not not with the environment.

Some physicists are pessimistic about the prospects of substantial experimental advances in the field[5]. They believe that decoherence will in practice never be reduced to the point where more than a few consecutive quantum computational steps can be performed. Others, more optimistic researchers, believe that practical quantum computers will appear in a matter of years rather than decades. This may prove to be a wishful thinking but the fact is the optimism, however naive, makes things happen. After all it used to be a widely accepted ``scientific truth'' that no machine heavier than air will ever fly !

So, many experimentalists do not give up. The current challenge is not to build a full quantum computer right away but rather to move from the experiments in which we merely observe quantum phenomena to experiments in which we can control these phenomena. This is a first step towards quantum logic gates and simple quantum networks.

Can we then control nature at the level of single photons and atoms? Yes, to some degree we can! For example in the so called cavity quantum electrodynamics experiments, which were performed by Serge Haroche, Jean-Michel Raimond and colleagues at the Ecole Normale Superieure in Paris, atoms can be controlled by single photons trapped in small superconducting cavities[6]. Another approach, advocated by Christopher Monroe, David Wineland and coworkers from the NIST in Boulder, USA, uses ions sitting in a radio-frequency trap[7]. Ions interact with each other exchanging vibrational excitations and each ion can be separately controlled by a properly focused and polarised laser beam.

Experimental and theoretical research in quantum computation is accelerating world-wide. New technologies for realising quantum computers are being proposed, and new types of quantum computation with various advantages over classical computation are continually being discovered and analysed and we believe some of them will bear technological fruit. From a fundamental standpoint, however, it does not matter how useful quantum computation turns out to be, nor does it matter whether we build the first quantum computer tomorrow, next year or centuries from now. The quantum theory of computation must in any case be an integral part of the world view of anyone who seeks a fundamental understanding of the quantum theory and the processing of information.
Bibliography
[1] R. Feynman, Int. J. Theor. Phys. 21, 467 (1982).
[2] D. Deutsch, Proc. R. Soc. London A 400, 97 (1985).
[3] P.W. Shor, in Proceedings of the 35th Annual Symposium on the Foundations of Computer Science, edited by S. Goldwasser (IEEE Computer Society Press, Los Alamitos, CA), p. 124 (1994).
[4] A. Barenco, D. Deutsch, A. Ekert and R. Jozsa, Phys. Rev. Lett. 74, 4083 (1995) [Available here].
[5] R. Landauer, Trans. R. Soc. London, Ser. A 353, 367 (1995).
[6] P. Domokos, J.M. Raymond, M. Brune and S. Haroche, Phys. Rev. A 52, 3554 (1995).
[7] C. Monroe, D.M. Meekhof, B.E. King, W.M. Itano and D.J. Wineland, Phys. Rev. Lett. 75, 4714 (1995).
Further Reading
A. Barenco, Quantum Physics and Computers, in Contemporary Physics, 37, pp 375-389.
A. Ekert and R. Jozsa, Quantum Computation and Shor's Factoring Algorithm, Review of Modern Physics, 68, pp.733-753, (July 1996).
D. Deustch, The Fabric of Reality, Ed. Viking Penguin Publishers, London (1997).

New spot, new names, new folks, new lies.


Enjoy.

AV