Quantum no-hiding theorem experimentally confirmed for first time

March 7, 2011 by Lisa Zyga, Phys.org feature

In part (a), the three qubits (the magnetic nuclei of hydrogen, fluorine, and carbon) are shown, with the quantum information stored in the first qubit. In part (b), the quantum information has been transferred from the first qubit to the third qubit. Image credit: Samal, et al. ©2011 American Physical Society.
(PhysOrg.com) -- In the classical world, information can be copied and deleted at will. In the quantum world, however, the conservation of quantum information means that information cannot be created nor destroyed. This concept stems from two fundamental theorems of quantum mechanics: the no-cloning theorem and the no-deleting theorem.

A third and related theorem, called the no-hiding theorem, addresses information loss in the . According to the no-hiding theorem, if information is missing from one system (which may happen when the system interacts with the environment), then the information is simply residing somewhere else in the Universe; in other words, the missing information cannot be hidden in the correlations between a system and its environment. Physicists Samuel L. Braunstein at the University of York, UK, and Arun K. Pati of the Harish-Chandra Research Institute, India, first proved the no-hiding theorem in 2007. Until now, however, the no-hiding theorem has been a purely theoretical concept.

Now for the first time, a team of physicists consisting of Pati, along with Jharana Rani Samal (deceased) and Anil Kumar of the Indian Institute of Science in Bangalore, India, has experimentally tested and confirmed the no-hiding theorem. The physicists have published their study on the no-hiding theorem test in a recent issue of . The work is dedicated to the memory of Samal, who died in November 2009 on her 27th birthday, and who performed all of the experimental work of the paper.

“In quantum information science, two fundamental theorems have been the no-cloning and the no-deleting theorems,” Pati told PhysOrg.com. “They bring out essential differences between quantum and classical information and are also intimately connected to the conservation of quantum information. However, these two theorems cannot be tested experimentally in the sense that these operations are not allowed by . (Since these operations are not allowed, we cannot implement them in the laboratory.) The best that one can do is to experimentally demonstrate the approximate cloning or approximate deleting of quantum information. (Note that the latter operations are allowed because you are not demanding exact cloning or exact deleting.) Now, the no-hiding theorem is a first of its kind, which is also related to the conservation of quantum information and can be subjected to experimental tests. In this respect, our experiment is also the first experimental test of a no-go theorem in quantum information. It is important to demonstrate experimentally whether the prediction of quantum theory comes true or not.”

The scientists performed the test using nuclear magnetic resonance (NMR), a technique that has previously been used to test other protocols, such as Shor’s algorithm and Grover’s algorithm, and is also used in magnetic resonance imaging (MRI). Here, the scientists used three magnetic nuclei of hydrogen, fluorine, and carbon from a large molecule (13CHFBr2). The three magnetic nuclei represent three qubits, one of which contains the original information, and the other two of which are ancilla qubits and are prepared in fixed states.

In order to make the first qubit “lose” its information, the scientists had to make the system undergo a bleaching process. In their experiment, they bleached the system through quantum state randomization, in which the qubit transforms from a pure state to a mixed state. Although the randomization operation causes the qubit to appear to lose the information contained in the pure state, the scientists showed that the information could be found in one of the two ancilla qubits. They also demonstrated how to use the ancilla qubits to reconstruct the original state, showing that no information was hiding in the correlations between the original qubit and the ancilla qubits, which is the essence of the no-hiding theorem.

“The greatest challenge for carrying out this experiment by NMR was the design of the pulse sequence for the ‘randomization operator,’” Kumar said. “This was achieved here by using a novel algorithmic technique developed in our laboratory by Ashok Ajoy (an M.Sc. student who has now gone to MIT, Boston, to do his Ph.D.). His method uses graphs of a complete set of base operators and develops an algorithmic technique for finding the decomposition of a given unitary operator into basis operators and their equivalent pulse sequences (to be published).”

In the future, the physicists plan to test the no-hiding theorem in more complex situations, such as in the context of coherent quantum teleportation, which will require the control and manipulation of a larger number of qubits. Overall, the quantum no-hiding theorem could have applications in areas such as quantum communication through private quantum channels, as well as black hole evaporation.

Explore further: Physicists Solve Difficult Classical Problem with One Quantum Bit

More information: Jharana Rani Samal, et al. “Experimental Test of the Quantum No-Hiding Theorem.” Physical Review Letters. 106, 080401 (2011). DOI: 10.1103/PhysRevLett.106.080401


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2.5 / 5 (4) Mar 07, 2011
Gosh this really important break trough , hope further experiment follow..
2 / 5 (3) Mar 07, 2011
I'm not a physicist but somehow this sounds heavy, consequential...would this mean if we in the future ripped a quantum MP3 it could never be erased or hidden again then? I don't think the media companies will like this much at all... Sad to read how Samal died.
3.2 / 5 (5) Mar 07, 2011
Samal's death is tragic and senseless - murdered, for refusing a marriage proposal. Indian society is a dichotomy of selfish archaic social behaviours and cutting edge sophistication in technical and scientific endeavours. Too bad. My sympathies for her family and colleagues. May she rest in peace.

* * *

Those who believe that quantum information can be neither created or destroyed should read about the work of Philip Bucksbaum, and this EETimes article: http://www.eetime...o-memory

1.3 / 5 (12) Mar 07, 2011
This article only increases my desire to invent Omni Scanners/Emitters (short for omniverse). That way I can bring my grandmother and mother back to life so I can see them again. I think I would prefer a younger version of them when they were hot (don't ask me why), but I wish for the most recent version of their memory. However, their souls have gone on to where ever they belong and I do not expect to see those copies for a while, maybe.
3 / 5 (2) Mar 07, 2011
Does it mean that the information can not be multiplied? I mean no illegal copies?
2.8 / 5 (4) Mar 07, 2011
information cannot be created nor destroyed -- but it can be scrambled by the random noise you forgot to isolate it from.
1 / 5 (2) Mar 07, 2011
Overall, the quantum no-hiding theorem could have applications in areas such as quantum communication through private quantum channels, as well as black hole evaporation.

Black hole EVAPORATION????? Someone please tell me what the hell they are talking about there.

Also to answer you question Question. I would say the that the singularity is a quantum state in of it's self. There for the no hide theory implies that any information passing into the quantum singularity can not be destroyed. Singularities may simply redistribute information across the universe. They could be the rabbit hole to the quantum world. In you go where and how you come out nobody knows.
3.5 / 5 (4) Mar 08, 2011
But how can information survive in the singularity of a blackhole?

Information is carried away through Hawking radiation. Any matter falling into a black hole becomes Hawking radiation eventually. When this information is released is relative. On the edge of a black hole the time dilation is immense, compared to a distant observers perception of time, causing the illusion of a singularity.
not rated yet Mar 08, 2011
If information in the quantum world cannot be destroyed, what happens when a DNA molecule is hydrolyzed down to individual base pairs? (or is that still on our side of the so-called 'weirdness barrier'?)
not rated yet Mar 09, 2011
If we are able to extract information about prior entangled states, would it be possible to "interrogate" photons and particles coming in from outside the galaxy (presumably some having interacted with the dark matter halo) to gather data about what we can't see?
1 / 5 (1) Mar 16, 2011
I'm not a physicist either. Doesn't this data support the idea that the information has been "copied" or cloned to another qubit and that it has not been deleted?
not rated yet Mar 16, 2011
No. There is no copy. Transfers are not copies. If it was copied then there would be two of it at the same time.

Which is supposed to be against the rules in the quantum world.

not rated yet Mar 28, 2011
This sounds to me more like a universal nano bar code. Will be 10 or 20 years later to be usefull in, IDK, quantum "taggin"

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