Quantum Cookbook
- Van Warren
There is a new era of computing taking shape, that holds the potential to greatly revolutionize the way some problems are solved. Quantum computing: It is in the pre-vacuum tube, pre-Eniac, pre-Illiac phase right now. The question is, just how to go about it? There are lots of approaches, but most are exotic and difficult.

How about porphyrin rings? They work well for heme where they hold an iron in nature's ultimate quest for high baggage rates. Hemoglobin, a huge tetrameric protein is made of four subunits, themselves large, each which hold a heme ring, which holds an iron, which provides a single unit of charge to be delivered for cellular respiration. Like putting a penny on a tractor trailer for a coast to coast trip. Plants use porphyrin rings as solar collectors, where a magnesium provides a similar, but more stationary role. These rings can hold zinc, copper, and a variety of metal ions. But forget that for a minute.

Today's strange idea is to take a 96 well biochemistry array and fill each well with its own drop of quantum fluid. When illuminated the quantum fluid in the well would undergo a superimposable and  reversible (like a CD-RW) state change. Superimposable means that the state changes accumulate without interfering with the previous state change. Each well would be the target of a set of lasers, in read/write pairs.  The wells, which would correspond to qubits, would be illuminated for reads and writes by a small mirror vibrating at high frequency (like the TI DLP micro mirror arrays used in digital projectors for example). The DLP mirrors would be controlled by a conventional digital signal processor (DSP) for setting up the problem. Quantum computers hold great promise for combinatorial problems of economic consequence that are currently considered incomputable, like Traveling Salesman Problem, or factoring a 1000 digit number. The latter would take longer than the estimated age of the universe. Very useful for code breaking those bad secret agent messages before its too late, and also for bringing security as we know it to a standstill. But hey, with progress comes problems.


The description above is fast and loose, but it does suggest some interesting questions. What fluid can absorb a state change in a reversible way? How many bits of change could be reversibly absorbed by a given fluid. If the fluid consisted of vibrating strings in suspension, how many modes of vibration could be supported reversibly? Would refresh be necessary? Dyes like to preferentially absorb laser light. Could a transformed dye be pumped to another well to continue the computation?


Vibrating strings in suspension is exactly what molecular bonds are. Would this require low temperature, so low that the vibrational modes are not deconstructed by heat and collision? Could long polymers of DNA, or similar plastics, be used that can be clipped to exact length using restriction enzymes? Can you sustain a mode of vibration on a polymer string? How about multiple modes with multiple notes? How long will a given polymer ring a given note? Can you anchor one or both ends of a polymer string using the famous biotin strepavidin bond? What about using quantum dots which are used to label DNA. Suspend the dot using double strands of DNA . Or we could borrow the hemoglobin/chlorophyll trick where a porphyrin ring holds the jewel of an iron or magnesium or copper or zinc to get its electrons rung once in a while. Whatever we do, we must preserve the coherence principle that allows the accumulation of multiple states.

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Would qubit computation take place more reliably in the solid state? Materials that can absorb photons or emit photons corresponding to an electronic or nuclear spin change are candidates. Flipping protons takes place at RF frequencies. In the optical realm each well would represents a hologramic bucket of data, as accumulated states. If you break off once piece of a hologram, you are still left with the whole picture, with the loss being in signal to noise. What does SNR mean in that case?


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Is the well half empty or half full? In a proper thinking process, and a quantum computer, it is in both states, simultaneously. I wonder if cells use that. I think they do.




References: Qubit.org


Keywords: quantum computing, holography, light emitting compounds, solid state lasers, DSP controlled lasers.


http://www.acm.org/technews/current/homepage.html: Volume 5, Issue 528:  Monday, August 4, 2003




Bridging the gap between quantum and desktop computers is the goal of University College London materials scientist Marshall Stoneham, who has received 3.7 million pounds to flesh out a quantum device that calculates efficiently, functions at higher temperatures than competing machines, and can be assembled with existing equipment. Current quantum computers can store and manipulate quantum bits (qubits) either by exploiting an ion's energy state or using the spins of atomic nuclei to represent 0 or 1: However, a quantum computer based on the ion manipulation approach is extremely large, while an nuclear-spin-based device requires magnets cooled by liquid helium, and cannot handle qubit increases past a certain point because the noise from neighboring molecules can mask the result signal. A design for a silicon-based quantum computer was proposed in 1998 by Australian researcher Bruce Kane, who theorized that phosphorus-impregnated silicon could yield a device that stores qubits in the spins of the embedded atoms' nuclei; the spins themselves would be flipped by radio signals, while the interaction between neighboring atoms would be reconciled by an electrode, enabling linked qubits to perform operations. Such a design could supposedly contain thousands of qubits that would be manipulated by existing electronics. Kane's proposal inspired several attempts to build a silicon-based quantum computer, including an Australian effort that has yielded top-down and bottom-up construction strategies and has modified the original concept to manipulate electron spins rather than nuclear spins. Stoneham's proposal would randomly distribute the embedded atoms within the silicon and employ laser light to manipulate electron spin. Qubits would be connected with "control atoms" that, like the qubit electrons, can be excited by specific laser-light frequencies. Stoneham thinks his quantum computer should operate at temperatures above 4 K, and anticipates a working three-qubit system by 2004 and a processor featuring tens of qubits by the end of the decade.