Showing posts with label quantum. Show all posts
Showing posts with label quantum. Show all posts

Ion Teleportation Scheme Could Scale Up Quantum Computers


By Saswato Das


Scientists have teleported the quantum state of one trapped ion onto another a meter away

23 January 2009—A team of scientists is announcing today in the journal Science that in one of those bizarre demonstrations of quantum mechanics it has managed to teleport the quantum state of one ion onto another across a distance of a meter. Though we’re accustomed to thinking of the Star Trek version of teleportation, what physicists call teleportation is the exact mapping of one particle’s quantum characteristics to another distant particle. That matters because future quantum computers and quantum cryptography networks need some way of storing data and moving it around.

In the past decade, physicists have shown that teleportation is possible with magnetic fields, photons, and even atoms. What makes the new results—by Christopher Monroe of the University of Maryland and his colleagues—interesting is that the team uses a hybrid approach involving both atoms and photons that fits well with quantum information networks and quantum computers. Theoretically, Monroe says, the technique they have invented can be extended to distances as great as thousands of kilometers, although all they have demonstrated so far is one meter.

Raymond Laflamme, director of the Institute for Quantum Computing, at the University of Waterloo, in Canada, called it “a very neat experiment and important milestone, demonstrating very good quantum control and bringing quantum teleportation one step nearer to practical applications.”

At the heart of teleportation lies a quantum mechanics effect known as entanglement. That phenomenon allows two particles—such as photons, atoms, or ions—to be linked in such a way that if someone measures the quantum state of one object, the state of the other becomes known as well. Entangled photons are often used in experimental quantum information networks. But while photons are easy to transmit (after all, they move with the highest speed in the universe), they are very difficult to store. On the other hand, atoms and ions preserve entanglement for a long time, but being massive, they are much harder to move from place to place.

The beauty of Monroe’s approach to teleportation is that it is an intelligent combination of the strengths of photons and ions. His team used two ytterbium ions confined in electromagnetic ion traps and cooled by lasers. The goal is to teleport the quantum state of one ytterbium ion to the other. Both ions are prepared for entanglement by microwave pulses and then zapped by ultrafast laser pulses. Each ion subsequently gives off a photon, which is entangled with the ion’s state. Through a complex series of steps, the system transfers the quantum state of one ytterbium ion to the other.

Norbert Lütkenhaus, of the Institute for Quantum Computing, says Monroe’s approach “make sense.” He says that “this technique allows them to couple ion traps in this optical way.”

Monroe says the hybrid approach will enable the creation of quantum repeaters—still-theoretical devices needed to make large-scale quantum cryptography networks—and will also be useful for making quantum computers. His group’s design for scalable quantum computers is to build multiple ion traps on a chip. The ions act as quantum bits and can perform computations when placed close together in a trap. However, to get the result of one trap to a computation in another trap without some sort of teleportation would require the difficult task of moving ions around on the chip. He says teleportation “may well be the most scalable approach” to building ion-chip computers.

Dick Slusher of the Georgia Tech Research Institute, isn’t so sure. “I think that in principle it is true that this teleportation process will facilitate scaling of quantum computation,” he says. “However, there are many ways to accomplish this scaling, including ion transport and error-correcting pulse sequences. Teleportation may well turn out to be the key process for scaling, but I think it is far too early to be sure of this.”

Life after life

Bryan Appleyard | January 19, 2009

Article from: The Australian

You are dying.

Twenty seconds ago your heart and breathing stopped and your pupils became fixed and dilated. Your brain cells are in a state of panic, trying every trick they know to get hold of oxygen and glucose. An electroencephalogram (EEG) would show no electrical activity in your cortex, the thin outer layer of your brain. You have flatlined.

As usual, a young, inexperienced doctor is first on the scene.

They’re fitter and faster. There’s only time to confirm you’re not breathing before starting 30 chest compressions followed by two breaths into your mouth. A cart arrives with a defibrillator, the electric-shock machine, as do a few older, less fit doctors. The machine is not, sadly, one of the sexy, telegenic ones with paddles and George Clooney shouting “Clear!” With this machine the electrodes are stuck to your chest. You are shocked. Nothing. A blood sample is taken and rushed for instant analysis. You’re given repeated injections of adrenaline and, depending on your exact condition, atropine, amiodarine and magnesium. Still nothing. The doctors and nurses work furiously for, say, 10 minutes if you’re an old lady with pneumonia, or half an hour or more if you’re a young man who’s fallen into a cold river.

Nothing. Finally, a watching consultant officially announces that you no longer exist. It’s over. The confusing babble known as “your life” has ended. Or has it? You see, the weird thing is that you may have flatlined, be “clinically dead”, but you’ve been watching the whole thing from the ceiling. As soon as your heart stopped, you just drifted out of your body and found you could float anywhere. You feel incredibly well, bathed in bright light, suffused with a deep sense of peace and knowing that, at last, it all makes sense. Some of your dead relatives are here and, behind you, there is a tunnel from which the light floods down. Perhaps you can see Jesus at the far end of it, or Muhammad or Krishna. The chaos at your bedside is interesting, amusing even, but trivial. Death, you now know with absolute certainty, is an illusion.

You’re having a near-death experience (NDE). They happen all the time. They may happen to everybody, however they die.

Remarkably similar experiences have been reported throughout history in all cultures. Obviously, most are lost to us, because being near death is usually the immediate prelude to being dead.

But precisely because high-tech hospital resuscitations are so effective – around 15 per cent of cardiac-arrest victims are revived – we can now regularly hear news apparently from beyond the grave. And it sounds like very good news indeed. You don’t really die and you feel great. What could be nicer? NDEs are so common, so vivid and so life-transforming – survivors frequently become more compassionate, religious and serene as a result of what they experience – that scientists, philosophers, priests, psychologists and cultists all want a piece of the action. Their problem is that the human mind is unreachable.

We can’t see what’s going on in there. Even if we could rush cardiac-arrest patients into an MRI scanner, we’d only see lights in the brain; we wouldn’t know what they meant.

But now NDEs are to be scientifically investigated in a US and UK study involving 25 hospitals. This is co-ordinated by Dr Sam Parnia at Southampton University in England and is designed to find 1,500 survivors of cardiac arrests – “clinical death” – who tell such stories. “I see no reason why a priest should tell us about death when we have all this technology available,” says Parnia.

“Death is a biological process and there’s no reason why we shouldn’t study it through medicine.”

Getting a scientific handle on this phenomenon is fiendishly difficult. Dead people don’t report back, and it is very hard to assess the status of survivor accounts – are they merely hallucinations occurring before the crisis or just after? Perhaps they are no more than the brain’s way of soothing your path to extinction.

Cardiac arrests are a good place to start because they provide a clear-cut moment when the dying process begins and when, clinically speaking, you may be said to be dead. Says Parnia: “It might in fact be better to say that experiences after cardiac arrests are actual death experiences rather than near-death experiences.” Cardiac arrests also happen a lot in hospitals, so the experimental conditions are reasonably controllable. But details such as bright lights, tunnels and feelings of peace cannot be pinned down experimentally.

One aspect of near-death experiences, however, can be: the out-of-body experience (OBE), seeing yourself and your surroundings from outside. When you are looking down from the ceiling, what exactly do you see? Many survivors report with remarkable accuracy what went on when they should, in theory, be utterly unconscious. This seems to be hard, testable evidence.

There are thousands of reports of OBEs but the two most famous cases are Pam Reynolds and Maria’s Tennis Shoe. Reynolds, an American singer, watched and later reported on with remarkable accuracy the top of her own skull being removed by surgeons before she moved into a bright glowing realm. But it was her account of the surgical implements used and the words spoken in the theatre that make the case so intriguing.

Maria, meanwhile, underwent cardiac arrest in 1977. She floated out of her body, drifted round the hospital and noticed a tennis shoe on a window sill.

It was later found to be exactly where she said it was. The shoe was said to be invisible from the ground and not in any location where Maria could have seen it. Such stories suggest that OBEs should be scientifically verifiable.

Parnia’s study is aimed solely at OBEs in cases of cardiac arrest. It uses a technique known as “hidden target”. In the participating hospitals he is placing pictures on high shelves so that they will be invisible both to patients and staff, but anybody floating near the ceiling would see them. There are numerous problems with this.

Parnia’s study does not have enough money to put laptops on the shelves generating random pictures to ensure that cheating is impossible. Furthermore, previous hidden-target experiments by, among others, Parnia himself and Dr Penny Sartori at Morriston Hospital in Swansea, Wales, have failed to produce a single positive result. In fairness, this may be because the last thing that a floating dying person, with Jesus behind him and his body being pounded in front of him, will notice is some odd picture left on a shelf. This leaves believers in OBEs with an evidential mountain to climb.

There are plenty of sceptics who will pounce on negative results or even positive ones with any signs of ambiguity. Dr Peter Fenwick, a neuro-psychiatrist who has overseen Parnia and Sartori’s work, admits that, whatever the outcome, there will still be “wriggle room” for sceptics.

“People can say they could have cheated, but if we have 50 or 60 of these cases where people leave their bodies and some see the pictures and some do not, then it looks like from the phenomenology that this does occur,” Fenwick says.

Hidden targets are the best key science has for unlocking the true nature of NDEs. If Parnia comes up with positive results, then even the most hardened sceptics will have to pay attention. They will force a serious rethinking of all current ideas about the brain and the mind.

This is definitely a legitimate scientific inquiry,” says Chris French, professor of psychology at Goldsmiths College, London, and co-editor of The Skeptic magazine. “Refereed proposals of this kind have my full support.

There’s no doubt that people have these experiences, and there is something of great psychological interest to be explained here.” French’s position is important. He specialises in paranormal beliefs and experiences. In some cases his position is that of outright scepticism. For example, people started reporting alien-abduction scenarios – flying saucers, anal probes – in large numbers only after a single case, that of Betty and Barney Hill, was publicised in Look magazine in 1966. This was clearly a kind of mental virus, made more virulent by the fact that most of the accounts were retrieved under hypnosis. But NDEs were widely reported even before they became known to a mass audience through Raymond Moody’s 1975 book Life After Life. And hypnosis has not been involved in retrieving the accounts.

The consistency and clarity of these reports across cultures and time zones convince French that, even if NDEs may not prove the afterlife, they do cast light on the human mind.

“There is a core experience that is essentially the same across cultures,” he says.

“Christians don’t see Hindu gods and Hindus don’t see Jesus, so there is some kind of cultural overlay, but we are dealing with people attempting to put an ineffable experience into words.

There’s a common core that has as its basis the fact that we all have very similar brains, so when things go awry we are likely to have similar experiences.” And, as in all things, it is the human mind that is at the heart of the matter.

If we can float out of our bodies, then the mind is separable from (and perhaps not dependent on) the brain. Twelve years after Tom Wolfe famously announced in Forbes magazine that, as a result of developments in neuroscience, “Your soul just died”, it may be time to say: “No, it didn’t.” But is such a thing as a separable mind possible or even conceivable? The answer is yes. In explaining why, it will be necessary to plunge into philosophy and quantum mechanics. Bear with me: at the end of it, you might just believe you are immortal.

The world, on the face of it, is made of two ingredients: thoughts and things. A brick, for example, is, on the one hand, a fact in the world and, on the other, a combination of all my feelings about bricks in general and this brick in particular. This is generally regarded as a very odd state of affairs. My thoughts and feelings are as real to me as the brick, but they don’t seem to be made of the same stuff. Indeed, they don’t seem to be made of any stuff. The belief that they aren’t, that the world is made of two different substances – bricks and thoughts of bricks – is called dualism.

Dualism is the default human conviction, embraced by religions, philosophies and, in fact, by everybody in their lives; if we didn’t embrace some degree of it, we’d be constantly worried about crashing our cars into other people’s thoughts. Dualism means that the mind and the brain are not made of the same things and therefore in theory they can be separated, as in NDEs.

Much of modern science can be seen as an attempt to disprove dualism.

In the strictly scientific world-view there is only one stuff out of which bricks and brains are constructed. My thoughts and feelings are just what the brain does. The brain gives us thoughts to provide the illusion of control. It’s largely an illusion that the mind has any effect on the world. We’re all imprisoned in the chains of cause and effect that started with the Big Bang. But in spite of numerous claims, this remains a statement of faith. Neuroscientists may be able to show what happens in the brain when we think or when we exercise “free will”, but this cannot be shown to be proof that dualism is wrong.

“Look,” they say, “we’ve proved it. It’s just neurons firing sparks at each other.” Well, no. Those electrical patterns are not thought itself; they may be no more than symptoms of thought. For all our technology, nobody has yet seen a thought, nobody has shown how matter becomes mind. How it does remains one of the most profound questions any human ever asks himself.

Enter quantum mechanics. This started as the study of very small things – subatomic particles. It is the most effective scientific idea ever: it powers your computer, television, anything dependent on electronics. So we know it’s true enough to work, but it’s also weird enough to defy belief. Everything about the discoveries in this area turned out to be in defiance of reason.

Crucially, two things were discovered. First, particles can continue to be connected to each other even though separated by long distances – billions of light years, even: a phenomenon known as non-locality.

This is, in our big world, impossible.

Second, quantum theory showed that the mind can affect the world. If, for example, you say that light is made of particles, then, obligingly, light will be particles. If you say it is waves, then it will be waves. The questions we ask of nature determine the answers it gives.

Anybody who claims to fully understand the ramifications of this is lying.

Henry Stapp must come close. He is a distinguished physicist at the University of California at Berkeley. He is convinced that quantum mechanics applies to large as well as small things.

The world as a whole is just as weird as the inner workings of the atom. The truth of the world and ourselves is that the whole thing is a chaotic swirl of energy and particles. But we don’t see it, because we make our own reality, our own truth, by only asking certain questions. The brick is a product of our mind; to all-seeing, non-human eyes, it is just a swirl of almost nothing.

“The observer,” Stapp tells me, “is brought into quantum dynamics in an essential way, not only as a passive observer but as an active part of the dynamics. He makes certain choices not specified by the physical dynamics which seem to come from the psychologically described realm rather than the physically described realm.

“So what happens when a person dies? Does this psychological part just fade away? That’s what most would think. On the other hand, there are these experiments done by physicians in connection with NDEs which seem to be evidence that brain-death or total brain inactivity does not totally put out the psychological aspect. The relationship between the brain and the psychic experience is not as simple as one might have expected.” On top of that, quantum nonlocality could mean the mind is capable of being non-local to the brain, of floating to the ceiling of the room. It can become, as Stapp puts it, “unglued”.

His words “certain choices not specified by the physical dynamics” are world-changing. This idea would, if widely accepted, end the reign of scientific materialism, replacing it with a new dualism. It would mean the universe is not a “causally closed” system, locked down since the Big Bang, as mainstream science has always insisted it is, but open to freedom of choice by the autonomous, floating, matter-altering mind. We would have regained our souls.

Positive results from Parnia’s survey might foreshadow the soul’s return.

The effects would be seismic.

First, you’d have to accustom yourself to the idea that your mind is not just the little man inside your skull – he really is out there in the world. Second, a lot of the things that now seem like products of charlatans – telepathy, spiritualism, even psychokinesis – will suddenly be much more credible. Third, you need not anticipate instant oblivion on death but a series of very weird and very illuminating experiences.

This would be a revolution, but it would also be a return to the past. Until the rise of secular materialism over the past 200 years, humans always lived with the conviction that the world was made of far more than brick-stuff, and they also lived with a lively sense of the presence of the dead.

But a bucket of iced water is necessary at this point. Few scientists think any of this is going to happen.

Believers in a new dualism – or, indeed, believers that there is anything more to NDEs than a psychologically interesting hallucination – are still a small minority.

The problem is that all the evidence remains anecdotal, and even the most impressive stories, such as Reynolds’s, tend to look less convincing on closer examination. “There are many claims of this kind,” writes the prominent psychologist Susan Blackmore, “but in my long decades of research into NDEs I never met any convincing evidence that they are true.” Sceptics such as Blackmore and Chris French may welcome the Parnia study, but others are less tolerant.

Attacks have been launched by hard sceptics against all of the most ambitious claims for NDEs. In The Skeptic, Jason Braithwaite of Birmingham University in England wrote a withering deconstruction of a headline-generating Dutch study that claimed survival of the mind after death. “(It) provided no evidence at all that the mind or consciousness is separate from brain processes,” he wrote.

“Their findings are entirely consistent with contemporary neuroscience and are in line with the general dying-brain account of NDE. It appears that the position of the survivalist is still one based on faith.” That, in a nutshell, is the mainstream position. What he means by the “dying-brain account” is simply that NDEs are just what happen when the brain starts shutting down; they may, indeed, be an evolved mechanism to console the psyche by distracting it from the intolerable prospect of its own extinction.

They may not even happen when the patient is flatlining but when he is slipping into or out of that state. As with dreams, it is often hard to say when they actually happen.
Or, even if NDEs do happen during flatlining, this may be due to deep brain activity undetected by an EEG, which only measures activity on the surface of the brain.

Furthermore, these type of experiences may not be such unusual events. Fighter pilots sometimes experience “G-Loc” – G-force-induced loss of consciousness, which produces pleasurable “dreamlets”, floating sensations and sights of family and as evidence of the truth of religion.

Elisabeth Kübler-Ross, a psychiatrist and counsellor of the dying, popularised this idea, and her conviction that the bright lights of the NDE were precisely what they seemed to be: a revelation of a divine plan. “In this light,” she wrote, “you will experience for the first time what man could have been. In this presence, which many people compare with Christ or God, with love or light, you will come to know that all your life on Earth was nothing but a school that you had to go through in order to learn special lessons.”

The sceptics say this is all nonsense, that whatever happens in your head when Clooney shouts “Clear!” is just another delusion generated by the material workings of that 1.3kg bag.

However, in the present state of our knowledge, this is crude and premature. We should not only wait for the results of Parnia’s experiment, we should also consider the deep weirdness of the world revealed by Stapp and quantum theory. Hard materialism is just one more philosophical position, and the authentic sceptical reaction is not a derisive snort but a humble acceptance that there are more things in heaven and Earth than are dreamt of in any of our philosophies.

Why quantum cryptography is gaining interest


from The Age:

Christine Evans-Pughe
October 27, 2008
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Quantum physics may come to the rescue of consumers - by using photons as a security key to beat bank card fraud. Christine Evans-Pughe reports.

If fraudsters copy the numbers from your bank debit or credit cards, there's little to stop them going on a shopping spree online. This kind of fraud - known as card-not-present - is a growing problem.

It could also be one of the first consumer applications to use quantum key distribution.

Quantum key distribution - or QKD - exploits the quantum mechanical properties of light particles (photons) to generate secret keys (strings of random numbers) that can be shared between two parties (for example, you and your bank) and used to encrypt data to safeguard it from snoopers.

Typically, QKD systems transmit a stream of differently oriented photons to represent 1s and 0s through an optical fibre or a free-space link. The snooper-proofing is intrinsic due to the fragility of quantum states: if you try to measure them they collapse, which is a marker for tampering, alerting the legitimate users to the presence of an eavesdropper.

Using quantum keys to encrypt data is, for now, of interest only to banks, governments and defence organisations, which might need to move lots of confidential information securely between sites.

But a recent demonstration in Vienna took the technology to a different level by integrating QKD into a standard communications network.

The event displayed VoIP, videoconferencing and web services that have been encrypted with constantly refreshed quantum keys.

It also included a prototype solution to card-not-present fraud, developed by Professor John Rarity from the University of Bristol and Hewlett-Packard Research Labs. The idea is that we would fill up our mobile phones or similar handheld devices with secrets (random strings of digits) at a quantum ATM. During online transactions, we would gradually consume this personal stash of secrets to encrypt information, such as our PIN, or to authenticate ourselves.

Hewlett-Packard's Tim Spiller says: "The quantum part gives you the promise that when you've topped up your secrets, only you and your service provider own this particular random digit string.

"If you're doing an internet transaction, you send the merchant however many secret bits [are] deemed to be secure. The merchant sends them on to Visa, say, who checks they're OK and if so, authenticates the transaction."

The Vienna event was the culmination of a four-year EU project called SECOQC (Secure Communication based on Quantum Cryptography) to bring QKD technology to the mainstream. The project partners - who are now defining a European technical standard - include Siemens, Toshiba, Hewlett-Packard, iD Quantique, the Thales Group and QinetiQ, as well as leading quantum scientists.

For the demo, Siemens installed seven quantum key links into a standard metropolitan fibre-optic communications network that runs around Vienna and connects several of its sites. The network had run successfully in test mode for several weeks now, according to Wolfgang Richter of Siemens.

Quantum keys won't be able to encrypt data traffic in real-world networks until standards have been finalised.

However, project leader Christian Monyk is optimistic, saying it could be produced in six months.

When, or if, consumers enter the picture is difficult to predict. Rarity and HP's technology is "on the banks' radars", according to Spiller. But the attraction of their system is that it's potentially very cheap.

HP's vision is that mobile phones could easily include half a short-range QKD system (which it says could be built from some standard LEDs and a low-cost integrated optical circuit).

"Getting that into the market would depend on demand but five years is reasonable," Spiller says.

Meanwhile, quantum cryptography is gaining interest. Last year, iD Quantique's simple point-to-point quantum key distribution technology was used to guarantee the security of votes cast in Geneva during the Swiss general election.

The defence and security company QinetiQ has been doing trials in London with network operator AboveNet, which provides fibre-optic connections for businesses. "We've done some experiments sending polarised photons through part of their network," says Dr Brian Lowans of QinetiQ. "We didn't have any hiccups."

The Guardian