Subject: Fishing in murky waters: Quantum computing
Date: Mon, 17 Jun 2002 21:28:22 +0300
From: "Dimiter G. Chakalov" <dchakalov@surfeu.at>
To: milburn@physics.uq.edu.au
CC: artur.ekert@qubit.org, rarity@dera.gov.uk,
     tapster@falcor.dera.gov.uk, paul.d.townsend@bt.com,
     adami@krl.caltech.edu, divince@watson.ibm.com,
     a.steane1@physics.ox.ac.uk, lkgrover@lucent.com,
     schmuel@informatics.bangor.ac.uk, Pieter.Kok@jpl.nasa.gov,
     pbenioff@anl.gov, bennetc@watson.ibm.com,
     William.K.Wootters@williams.edu, hughes@lanl.gov,
     hemmer@maxwell.rl.plh.af.mil, caves@tangelo.phys.unm.edu,
     jonathan.p.dowling@jpl.nasa.gov
BCC: [snip]
 

Dear Dr. Milburn,

In your recent article "Quantum Technology: The Second Quantum Revolution", quant-ph/0206091 [Ref. 1], you and your co-author Jonathan Dowling wrote:

"As yet there is no dedicated effort in quantum technology as such, and the field itself has only just begun to define itself as a discipline. However we are convinced that as these experiments move form the lab to the market place the emergence of a new discipline of quantum technology or quantum engineering is almost certain, and it is not at all too early to ask where the wise money should be invested."

Surely not in "quantum computing",

http://members.aon.at/chakalov/Dyakonov.html

To make a quantum computer, you have to keep the entangled state 'alive and kicking' for a finite time interval, as read with you clock,

http://members.aon.at/chakalov/Wald.html

NB: The target word in your article [Ref. 1] is "simultaneously". It seems to me that this is a privilege of the human brain only, for which two modes of time may apply,

http://members.aon.at/chakalov/dimi.html

If I'm on the right track, forget about "error-free quantum computing".

You also wrote: "The quantum cryptographic keys distributed in this fashion are provably immune to attack -- guaranteed by the Heisenberg Uncertainty Principle."

There is no guarantee here, simply because no one knows the nature of quantum reality,

http://members.aon.at/chakalov/right.html#Note_2

To understand the postulates in QM introduced 'by hand', which make QM a highly successful calculation tool eluding any intuitive understanding,

http://members.aon.at/chakalov/Khrennikov.html#Växjö ,

I believe we need new physics,

http://members.aon.at/chakalov/Adler.html
 

That is, quantum gravity,

http://members.aon.at/chakalov/Butterfield.html

Since we don't have it yet, I think it is quite premature to include the dream of "quantum computing" in the basket of all potentially viable quantum technologies.

I regret that this email will be automatically deleted by your co-author Jonathan Dowling,

http://members.aon.at/chakalov/Adami.html#5

and by Carlton Caves,

http://members.aon.at/chakalov/Adami.html#9

I won't benefit from their professional criticism, regrettably.

If possible, may I ask you to forward my email to your co-author, since he acknowledged "additional support" from the Office of Naval Research, the Advanced Research and Development Activity, the National Security Agency, and the Defense Advanced Research Projects Agency [Ref. 1]. I think the time has come to put his cards on the table. The sooner, the better.

I will appreciate your questions and critical comments, as well as those by your colleagues included in CC: and BCC: lists.

Please do not hesitate.

You can read this email also at

http://members.aon.at/chakalov/Milburn.html

Sincerely yours,

Dimi Chakalov
--
http://members.aon.at/chakalov
http://members.aon.at/chakalov/dimi.html
 

Reference

[Ref. 1] Jonathan P. Dowling, Gerard J. Milburn. Quantum Technology: The Second Quantum Revolution. Thu, 13 Jun 2002 21:25:08 GMT,
http://xxx.lanl.gov/abs/quant-ph/0206091

"The hallmark of this Second Quantum Revolution is the realization that we humans are no longer passive observers of the quantum world that Nature has given us.
...

"Thus, although quantum mechanics as a science has matured completely, quantum engineering as a technology is now emerging on  its own right. It is just a matter of being in the right place at the right time to take full advantage of these new development.
...

"The objective of quantum technology is to deliver useful devices and processes that are based on quantum principles which include:

. Quantisation (quantum size effect); the allowed energies of a tightly confined system of particles are restricted to a discrete set.

· Uncertainty principle; for every perfectly specified quantum state there is always at least one measurement, the results of which are completely certain, and simultaneously at least one measurement for which the results are largely random.

· Quantum Superposition; if an event can be realized in two or more indistinguishable ways, the state of the system is a superposition of each way simultaneously.

· Entanglement: the superposition principle applied to certain nonlocal correlations, if a correlation can be realized in two or more indistinguishable ways, the state of the system is a superposition of all such correlations simultaneously.

· Decoherence: what happens to quantum superpositions when an attempt is made to distinguish previously indistinguishable ways an event can be realized. It renders superpositions of probability amplitudes into superpositions of classical probabilities. Decoherence has no analogue in classical physics.
...

"Building a quantum computer is the greatest challenge for a future quantum technology, requiring the ability to manipulate quantum-entangled states for millions of sub-components. Such a technology will necessarily incorporate the previous three quantum applications for readout (quantum metrology), error correction (quantum control), and interconnects (quantum communication).
...

"From 1980 until 1994, the theory and experiments on nonlocal quantum correlations remained an obscure branch of the Foundations of Quantum Mechanics. However, all that changed with two breakthroughs in 1994, when two critical events took place that began the quantum information revolution. The first was the experimental demonstration, by a group at the British Defence Evaluation and Research Agency (DERA), that nonlocal photon correlations could be used to make an unbreakable quantum cryptographic key distribution system over 4 km of optical fiber [11]. The second was the theoretical exposition by Shor that a quantum computer, by harnessing these delicate nonlocal quantum entanglements, could provide an exponential speed up in computational power for some intractable numerical problems [12]. Thus, in 1994 the world learned that quantum entanglement was important technological tool and not just a curiosity.
...

"While quantum computing is still in its infancy, quantum cryptography is here and now. (...) Los Alamos National Lab (LANL) is currently working on such a free space system in the group of Richard Hughes. The quantum cryptographic keys distributed in this fashion are provably immune to attack -- guaranteed by the Heisenberg Uncertainty Principle. This result, when coupled with the threat quantum computers now pose to existing public key systems, gives a new quantum way of transmitting secure data, in a fashion that is proven to be unbreakable -- even by a quantum computer [15].
...

"In addition, quantum error correction codes are being developed all over the world to ensure error-free operation of a quantum computer, once the technology is in place [16].
...

"Compared to some of the other ideas in coherent quantum electronics, discussed above, the SQUID technology is already well developed. Still, there is much to be done, including the possible application to quantum computers. However, there is a serious roadblock that has yet to be overcome.
...

"Ultimately, molecular electronics may be able to utilise the self assembly that characterises biological systems, paving the way for a nanotechnology that mimics biological systems, a bio-mimetic nanotechnology.
...

"As mentioned above there has been considerable progress in harnessing superconducting quantum degrees of freedom for quantum information processing, and the first all solid-state qubit has been demonstrated in such a device [27]. A solid state quantum computer is probably the most daunting quantum technological challenge of all and will require huge advances in almost all the areas of quantum technology we have discussed.
...

"Commercial applications are even further away for many of the technologies, although there are some promising beginnings (quantum cryptography for example). As yet there is no dedicated effort in quantum technology as such, and the field itself has only just begun to define itself as a discipline. However we are convinced that as these experiments move form the lab to the market place the emergence of a new discipline of quantum technology or quantum engineering is almost certain, and it is not at all too early to ask where the wise money should be invested.
...

"One of the authors (JPD) would like to thank the Office of Naval Research, the Advanced Research and Development Activity, the National Security Agency, and the Defense Advanced Research Projects Agency for additional support."
 

======

Subject: Atom laser coherence
Date: Wed, 19 Jun 2002 16:00:01 +0300
From: "Dimiter G. Chakalov" <dchakalov@surfeu.at>
To: Gerard Milburn <G.Milburn@damtp.cam.ac.uk>
BCC: [snip]
References: 1
 

Dear Gerard,

I'm certainly optimistic about quantum technologies, although I haven't read your book. I don't work in this field, for obvious reasons,

http://members.aon.at/chakalov/MAVER.html

but I try to follow closely the publications relevant to atom laser coherence, such as [Ref. 1], and phase coherence in general [Ref. 2]. I believe the control of phase coherence is in reach of the human brain. You don't have to elevate stone blocks to build pyramids:-)

No need to reply, I just wanted to to say something positive, but it's still 'fishing in murky waters'.

Best regards,

Dimi 
-- 
Dimiter G. Chakalov
http://members.aon.at/chakalov
http://members.aon.at/chakalov/dimi.html
 

References

[Ref. 1] L.K. Thomsen, H.M. Wiseman. Atom laser coherence and its control via feedback.
http://xxx.lanl.gov/abs/quant-ph/0202027
Journal-ref: PRA 65, 063607 (2002)

See Sec. IV "Reducing the linewidth via feedback", and Sec. V "Summary", p. 12: "Basically, by feeding back the results of a QND measurement of the number fluctuations to control the condensate energy, it is possible to compensate for the linewidth caused by the frequency fluctuations. The very number-phase correlation created by the collisions is utilized to cancel their effect."
 

[Ref. 2] William A. Tiller. A White Paper on The Law of Cause and Effect. 
http://www.tiller.org/tiller6.html

"(b) Coherence:  To illustrate this principle, let us consider the case of a typical home-use 60 watt light bulb (~1 watt/cm3).  It provides some illumination but not a lot of illumination. This is primarily because the emitted photons destructively interfere with each other so that most of the bulb's potential effectiveness is destroyed.  However, if we could somehow take the same number of photons emitted by the light bulb per second and orchestrate their emission to be in phase with each other, then we would have constructive interference between these photons (a laser) and now the energy density of the surface of the light bulb would be thousands to millions of times larger than that emitted by the surface of the sun (~6000 watts/cm2). This illustrates the unutilized potential in the present light bulb.  Perhaps the best example of the development of coherent energy emissions from humans comes from studies of QiGong masters [1]. They appear to emit beams of infra red radiation (~1 to 4. 5 microns) from their palms that have healing benefits."

[1] W. A. Tiller, Science and Human Transformation: Subtle Energies, Intentionality and Consciousness (Pavior Publishing, Walnut Creek, CA, 1997).


Note: In the summer or autumn 1947, H.B.G. (Hendrik Brugt Gerhard) Casimir mentioned his results to Niels Bohr, during a walk, and Bohr "mumbled something about zero-point energy".

This "mumbling" led to the discovery of the cohesion energy (cf. G. Jordan Maclay, Heidi Fearn, and Peter W. Milonni, Of Some Theoretical Significance: Implications of Casimir Effects, quant-ph/0105002). See also:

Peter W Milonni, Controlling the speed of light pulses, J. Phys. B: At. Mol. Opt. Phys. 35 (2002) R31-R56; pdf file from here. See Sec 6, Propagation of energy, p. R48: "In considering the velocity vE of energy transport it is imperative to recognize the simple fact that part of the energy density is stored for a finite time in the propagation medium."

Also p. R54: "It is nevertheless fascinating that quantum mechanics seems to go 'right at the border line of contradicting special relativity, but does not cross it' [10]."

Following Niels Bohr, I mumbled something about the Holon here. See also:

J. Maclay and R.L. Forward, "A Gedanken spacecraft that operates using the quantum vacuum (Dynamic Casimir effect)," Foundations of Physics (to be published March issue 2004); pdf file from here.

I sent my proposal to DOE in March 1994. It's such a terrible waste to burn oil... but that's my silent mumbling. Instead, we chose Operation Freedom for Oil, sit venia verbo.


D. Chakalov
August 30, 2004