Logic gates and illogic thrusts in quantum computing.

Quantum computer is probably the most prominent subject of quantum physics. Reason is obvious. While all the mystifying test results in quantum mechanics only seem to bug people's minds, quantum computers would put all this confusing potential to maximum benefit. Increasing endeavor to produce quantum computers has already grasped mainstream public attention, which is not very commonplace situation for futuristic technology. Even some people who don't have any particular interest in physics may have heard of qcs and started to adapt the idea. This may result less than usual resistance towards this new technology once it appears.

Early acceptance towards qc would be beneficial to everyone.*

Computers we use today speed up almost constant rate. In the progress bulgy relays has transformed to notably large vacuum tubes to sole transistors and to integrated circuits holding many transistors in a single chip. And while still integrated circuits are the building bricks of modern computers, Moore's law has pretty accurately predicted that amount of transistors on integrated circuits doubles every two year. Key feature to achieve this has been the size. Technology manufacturers has been able to miniaturize transistors so that more and of them will fit into single chip. This very handsome trend has unfortunately limits however, one of the most obvious one is that when transistor reaches size of an atom it cannot be divided into smaller pieces. More likely that small transistors won't be ever be achieved, because when the quantum rules begins to place in the small realm of tiniest chipsets, whole new formation of rules and phenomenons are required to be considered in the manufacturing process.

Classical transistors themselves act as logic gates in computer chips. Logic gates are like small counters who can count to two using Boolean algebra. Well, to tell difference between values 0 and 1 to be accurate. These values could represent basically any physical property that can be measured, voltage of electrical current for example (≥5V = 0; 7V≥= 1). There are many different kind of gates available, but ordinary computer doesn't have to have all of them in order to be universal (universal means it can compute any possible binary code). Quantum computers would have to have major difference in it's logic gates, since data wouldn't be processed in any certain state using quantum bits (quantum bits = qubits I mentioned in my previous text).

AND logic gate's and NOT gate's truth tables. AND gives out 1 if both inputs are 1, otherwise it gives 0. NOT gate always changes input, therefore it is common called inverter.

Notice how you could guess what was the input in NOT-gate if you knew only output? Well same is not with AND-gate. You cannot tell if A or B both were 0 or if only one of them was 1 if output is 0 You loose some information when you move from input to output. Logic gates in quantum computing would have this thing differently and it's one the reasons why theoretically qc is faster than ordinary computer. However it would be faster only in some processes and not so smooth in others. Much like an airplane is faster so long as it stays airborne.

Early qc pioneer Edward Fredkin came up with idea for logic gate for qc. Fredkin had a dream of building a reversible computer and he realized that this can be achieved if no information is lost in a logic gate. Truth table in Fredkin gate looks confusing at first, put if you pay attention to it, you'll notice that c value never changes when it move trough the gate. Also notice other two values p and q don't change when c = 0, and they switch places if c=1. Fredkin gate is universal and completely reversible.

Fredkins gate is an example of logic gate in quantum computer.

When I wrote Fredkins gate is reversible, it means that it can undone itself without consuming resources. This is not possible with ordinary transistors. However if qc is build to use physical properties that are entangled, like spin or polarization, it is possible to have logic gates that puts spooky action at a distance into better use than confusing Einstein. Swapping from input to output and from output to input without consuming time or energy, quantum computer could provide answers to questions which are presently thought to be unsolvable, thrusting mankind's capabilities into new highs, beyond quantum barriers which seem to separate our world from another, smaller, but more potential one. 

2>2 or: How I Learned to Stop Waiting and Love the Computer

The fuss on quantum computing has been quite excessive considering it has been going on for almost 40 years now. Quantum computer (qc) has been accepted as a likely future innovation around in the 80's and has been expected to pop up sooner or later since that. Early pioners of qcs were pretty much living in the blind spot of the scientific community, until Richard Feynman got interested in the qcs. He had already that point won a Nobel price and was altogether very influential scientist, so he was able to raise the general interest in the qcs in hes speech in MIT - conference.

What would it do then?

Whole concept of quantum type of information technology is staggering all the way beyond the imaginable. Scientist have made such promises about qc that they would change the world at once and for good. Back to the title of this post. One may ask: What could quantum computing possibly offer if it uses basically same binary code than in ordinary Turing machine? Line of zeros and ones. The thing is that they are not the same numbers 0 and 1 since the code would the superposition of each other. Quantum bit is actually called qubit for that. Since the line of code would be in the superposition of all the other possible lines of code, this qc would answer all the possible variations of questions simultaneously. On the contrary classical computer could have to done that same thing, but time consumingly.

First commercially successful quantum computer might look like this.
Shuttle at The Intrepid Sea, Air & Space Museum, New York.

The fun part of waiting these quantum computers is that nobody can't predict what the first truly successful qc looks like, or what technique it uses to produce qubits. The thing is that quantum mechanics provide numerous of ways to produce qubits. Basically any physical property that can be in superposition could be used to simulate qubits. So first Quantum-pc could have mirrors and lights and qubit would be the superposition of photon polarization. Or it could be using spin of a electron or why not spin of a nuclei. Several other possibilities is already know today.

Taking into consideration numerous ways to build a qc, and the time that has passed, you might ask what is still holding back development of quantum computers and why aren't they everywhere yet? Well, it's still possible that quantum computers will never take place and even when they eventually do, they won't make classical computers obsolete. It is because they do different things better. Much like classical physics does some things better and quantum physics other things. You wouldn't want to use quantum mechanics to build a entire car or boat. Trust me, you really wouldn't.

Further reading: Minds, Machines and Multiverse: The Quest for the Quantum Computer by Julian Brown.

Eventually there needs to be more than one

Scientist have always dreamed of one big, one exclusive, all-inclusive, exact theory that would cover anything that there is needed to be know of universe. This is good but surely not sole example of conflicting wish, which would make the actual wisher dispensable, when wish would come true. Luckily for scientist, universe seem to offer the more surprises and paradoxes the more you research.

Grand unification attempts

As tempting as it would be, one rigorous unification theory would have downsides too. Physics have fed the development of technology, industry, economy, political societies and even human interactions. Achieving suddenly the ultimate finish in physics would slow down scientific creativity in those other fields too. Those are fields that cannot necessarily reach "the ultimate pinnacle" and they benefit more from progress rather than from getting to the finish.

Modern societies are based on technology.

Nowadays The Standard Model is often considered the most profound scientific theory covering pretty much everything. Well, almost everything except that one bad old news, gravitation. To my opinion standard model or any other model cannot cover every measurable property without being conflicting with itself. My argument is that if every measurement contain inaccuracy (Heisenberg's uncertainty principle), modelling single particle shouldn't be done with same method that is used in modelling huge amount of particles. Increasing the amount of particles in the model would increase the amount of error in measurement drastically. Thus modelling huge group of particles would be measured more accurately when they are measured as a group instead of individuals. Nature sets us limits how she lets information be extracted from her.

Or maybe things actually start to behave differently when they are put together and therefore there even cannot be one theory for the small and for the big. Also big problem of these wide angle theories is that every one smallest detail must be completely and fundamentally correct and interpreted perfectly. If there is a even small flaw in the philosophy in the smallest scale scenes, error is brought up and enlarged to macroscopic level too. And sadly there is not (well at least not yet) any way to study and measure anything that is much smaller than femtometre (10^-15 m).

Things smaller than scale mentioned before are products of rationing and philosophy. Thus they are in a way also matter of believe and might needed to be rethought once in a while new scientific information is discovered or new revolutionizing ideas are brought up. Once in a while brilliant scientist manage to engineer new test setups to research beyond familiar boundaries. Scientist who manage to contribute via thought experiments are usually already refined in public. This has happened many times in the history of science and is especially active now in CERN - organization.

But in the end what distinguishes belief systems from science? To my opinion it's that you recon that you could be wrong, and you keep your mind open and prepared for new ideas if they offer better, less paradoxical description of nature than those what we had before. The key point is to collaborate and to stand on the shoulders of a giants instead of trying to gain authority or personal benefit via knowledge.

The illusion of time and does it have an arrow?

I decided to continue on the subject of time on this post for it's such a rich source of philosophical ponder and paradoxes. Time is too complex term to be described as a line, line of historical events until the time stops into the moment you recon as the present. Humans have intuitive hunch, similar as described above, of the nature of the time, which is linked with consciousness. Yet when the concept of time is put under scientific though, interpretation of what time is or can be start to straggle.

Time is a good companion of scientific diagrams. When you have one scientific quantity on one axis of Cartesian plane, it's in many cases informative to have time on the other. Still nobody cannot exactly tell what is time. A moment which is passed before you could really get hold of it? Maybe a periodic function in which phase is the only thing that truly matters?

The more you stop and think about time the less it makes sense. Then after awhile you realize you've been thinking quite a long time.

After reading Etienne Klein's Conversations With the Sphinx book I truly realized how incredibly complex and irrational the concept of time is. Time seem so familiar and essential thing that it is hard to accept that there is not a "right" scientific way to picture time. Perhaps the most important issue about time is that some events suggest that time is irreversible and other suggest that it is reversible. In other words it's a battle of a line like, and universal and dynamic time. Surely it can't be both at the same time?

Entropy as far as I know points out the direction of time and suggest that there is only one way to go. Then again many quantum mechanical processes (like strong interaction) can occur "both ways" and entangled photons can somehow transfer information instantly, reacting as if they were liberated from the tides of time. One could state that time marches on and swings back and forth simultaneously.

The basic unit of time, second was originally defined by the earth's orbit period around the sun. Nowadays it's about "the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.1" So we have gone from huge macroscopic event to theoretical (since ground state means 0K) quantum mechanical event that is basically a matter of probability. These two cannot really be compared, still they both have posed as the ultimate description of nature.

Even though for us humans time seems to be lost for good once it's gone by in our macroscopic world, quantum physic suggest even that the time travelling could be possible someday. Well at least for a single particles according to Wheeler and Feynman. This following video will show you why this time travelling would be a very bad idea if it could be executed in a human scale: http://www.youtube.com/watch?v=75nBenOWul0

Lead us to the new age, chosen one

Ancient time, modern times. Prehistory, contemporary history. We have many different names for different times. These classifications are usually overlapping, subject of debate and sometimes not all that scientific. They however make our perspective towards our past more meaningful. Efforts made today will lead to brighter future in contrast to what world used be.

Innovations are usually considered to be the fuel for advancing into a new age and at first glance it really seems to be that way. Watt's steam engine triggered industrial revolution, advances in metallurgy led to iron age and so on. Any more detailed analysis will fall flat any fantasy of sudden intuitive leap in development of the history of mankind.

Watt's steam engine was an improvement to Tomas Newcomens engine which wasn't the first steam engine around either. Iron age has been scaled between 1200 BC - 700 AD varying in different locations(1). But then again, iron was acquired from meteorites already couple of thousand years before 1200 BC and smelting technologies slowly evolved without any certain dramatic event. Some even suggest that the shortage of tin used in bronze alloy forced bronze smiths to seek alternative natural resources thus leading mankind to another era because simply it needed to happen.

Past is history. But when does time stop being the present? Picture taken in 2009 at a dock.

Let's skip to time being

What about now? Where do we stand now? Information age? Well I'm writing my thoughts to be published in the world wide web. That has certainly changed since industrial age. If I lived in the 19th century I could only hand out these silly thoughts in leaflets on the streets in Finland. There is however not a single innovation that would make the difference between industrial and information age. And there won't be a single magical event that will make the difference between this information time and the next one. More important will probably be the social aspect. The new age will already be there when it's wanted and needed, whatever it will be called. Maybe a quantum age? Yeah, I vote for quantum age.

There innovations for new age are already here. LASER for example is device based on a quantum phenomena. It has revolutionized communications but it has not revolutionized the way we common people look at the world or ourselves. Scientist have also performed magical things like teleportation in laboratories. These are particularly those kind of examples that cannot be explained using previous classical ideas, suggesting that there is a need for a turn of a page. Perhaps when man discovers practical ways to exploit entanglement and superposition in computing, historians will mark a point for new era.

I cannot predict the future but eventually we are forced to accept that our description of the physical world has not been complete. And that is the point we start to look at the past as if it was a "different" era than we presently live. I cannot but wish to live long enough to experience that exiting turn up, which will occur indistinguishably. There is already proven theoretical basis for the turn up in quantum mechanics, but perhaps it still lacks a proper practical interpretation for it. 

Never mind the balls, here's entanglement

To me, greatest coincidence ever occurred is this planet we live on. For some reason life happened, creatures emerged and evolved. Along came humans, us. Ironically world produced a creature which is able to study reasons for it's own existence. Were we put here to find out why we were put here? That question may be closer to theology than science but I think that as long as you don't stop asking questions your soul is doing just fine. Luckily world has almost infinite amount of riddles for a curious mind.

Liverpool rules the waves, powerful advantage indeed.

I'm not sure what I was thinking of that sculpture at the time I took the picture above but now it resembles particles with entangled spin to me. Spin is a property of a individual particle that can be described as a angular momentum. But not like the angular momentum as in common sense world. When you spin me Round Like a Record (Another accidental quantum physics reference pointing to Liverpool) I could have one well defined angle while spinning around my hypothetical axle. Same doesn't go with the quantum world.

In the quantum world spin is a weird mathematical phenomena which raises more questions than it answers to. Spin can have only certain quantized values times ħ. Particles that have spin number half-integer are considered drastically different than those which have integer as spin number. Those particles that have half-integer are called fermions and those integer ones are called bosons. It's hard to describe or even imagine what does it means in practical terms but the important bit is that fermions (e.g. electrons) can't be in same quantum state and bosons (e.g. photons) can.

So for example electron has a spin of 1/2ħ which means that if we draw electron spinning around it's axel, that axel could point either up or down (much like those two balls in the picture). If these balls were close together they would interact and become entangled. This entanglement would cause the other ball to spin up and other down, since same quantum state would not be possible. Also no other balls could join in the party because there are only two possible orientations and they have been taken like seats. This is actually the reason why there is electron orbitals around an atom. When first two electron occupy space around nucleus, they get entangled and reserve all the two possible quantum states. If other electrons also wish to join in they will have to go further away from the nucleus to avoid the quantum state of those two which were there first.

Bosons can get entangled too, and spin is not the only property that can get entangled. But the most unimaginable thing about entanglement is that when you separate particles they still stay entangled. That may not sound that much of a big deal at the first thought but it can basically permit a way to communicate faster than light travels. Just send one photon from space station to polarizer in France and other to moon (cheap and easy), you would instantly know in which angle polarizer is on the moon by looking at the polarization results in France. So information on the moon was acquired faster than the light would travel from moon. And since nothing travels faster than light, we have this thing called dilemma. 

How small can you go?

In the course of scientific advances man has gained ability to look ever deeper and further. Fundamental idea that there will eventually be one smallest piece of matter which cannot be divided into smaller ones is astonishingly old. In matter of fact that idea is quite ancient. It dates back to c. 400 BCE and it was, if not invented, at least promoted by Greek philosopher Democritus and his mentor Leusippus. Of course much has changed in the way to pursuit the tiniest particles. Still one cannot but wonder how come people 2500 years ago already come up with same hypothesis that scientist today claim with the help of their modern equipment.

Nowadays scientist have named and categorized at least 25 "fundamental" sub-atomic particles some which, like protons, are already believed being composed of even smaller pieces called quarks. Higgs boson is the latest entry in this group of sub-atomic crew. And there's not clearly a stop for detecting and adding yet more particles.

Smallest theoretical length, so called Planck length is 10^-35 m and size of a electron is less than 10^-15 m. So theoretically even smaller sub-sub-atomic or sub-sub-sub-atomic structures are possible. However it is getting harder and harder to research anything smaller than what has already been found out because of the uncertainty principle. More accurate measurement changes the reality of particle-on-measure further.

Would you reproach?

When we focus our mind on the tiniest scale in the quantum world along comes the concept of probability. Our everyday life can be relatively well predicted because we can measure our clumsy movement by dividing it into smaller pieces and different forces. But eventually there will be a limit (no matter if it has been already reached or not!) that you cannot divide movement or matter into smaller components. Then the only thing that is certain is the probability. Some people find this idea troubling. But they really can't do anything about it, they just have to live with it. This probability is the fundamental description of nature when we look at the double-slit experiment or in puzzling quantum entanglement phenomena.

I have already written few thoughts on double-slit experiment, but haven't mentioned the concept of probability in it even thought it seems to be quite fundamental part of it and whole quantum mechanics. Quantum mechanics state that a particle is in a "Probability distribution" and cannot be located in any precise location before it has been measured. Einstein for example never accepted this and once famously said "God doesn't play with dice." Considering the fact that probability waves give precise accurate prediction in numerous test settings and explains many concepts like quantum tunneling I have to agree with him. God doesn't play with dice, god IS a dice.

Clip art examples of different shaped and colored gods... I mean dices.