by Today we are going to talk about an extremely important development that has taken place in the science of quantum computing. The history of this is intertwined in many ways with the history of industrial knitting itself. One of the most important knitting patents was the “Jacquard machine”, in 1804. It was a set of components that allowed a mechanical loom to weave any pattern from a set of son. All that was needed was to feed the loom with a series of punched cards that coded the weave, changing the weave being no more complicated than simply changing the deck of cards. Although not the only one, it was a crucial development in the industrialization of textiles, which in turn was a major step in the industrial revolution.
We find the same punch card logic in a new role at the dawn of the computer age. In an identical philosophy, a program was written in the form of a series of punched cards, the holes and the untouchable dots encoding the program in the form of a series of “1”s and “0s”, i.e. that is, the language common to all computers. However, the connection between knitting and computers doesn’t end there. Early versions of computer memory consisted of metal elements strung on a grid of wires. They didn’t just look like knits, but they were: NASA had hired former textile workers through Raytheon to use their experience to “knit” the memory used in the Apollo vehicles. [α, β].
The next step in computing is quantum computing. By using very small, extremely well-isolated systems of individuals for computation, we can “choreograph” a program so that all paths to wrong answers cancel out and only the right answer remains. So far we know how to do such “choreographies” for a few specific categories of problems. But in them, quantum computers easily solve problems that a supercomputer would not solve even if it had worked continuously since the beginning of our universe. It is no coincidence that a significant part of cryptography protocols is based on such problems (unsolvable for classical computers), and there is strong scientific interest [γ] and a financial interest in them.
The reason why quantum computers are not part of everyday life is precisely the extreme sensitivity of their arrangements: if the “quantum bits” interact slightly with the environment, they lose all their useful properties. For this reason, experimental quantum computers so far can maintain their operation for short periods of time and consume a significant part of their capacities to discover and correct the resulting errors. This is not helped at all by the fact that in the microcosm the particles are identical. If we have two particles in front of us, close our eyes and someone swaps their positions twice, it’s impossible to understand. Making an analogy with an empty knitting machine, if we leave the room and return to it, it will be impossible to tell whether it worked while we were gone and simply returned to its original position.
At this point come two very important releases from the Google team [δ] and the company Quantinuum [ε]. Both succeeded by using a special form of “virtual particles” that appear when we limit quantum bits to a level called “non-abelian anyons”. Using the previous analogy, it’s like feeding the machine with yarn: if we leave the room and come back, we can tell if it has moved or not by seeing if it has produced any knitting. According to one interpretation, these particles remain identical to each other, but if they move they produce “knots” in spacetime.
This entanglement can be measured, opening a new avenue for efficient error correction of quantum computers. Such a development, using a kind of virtual particles which until recently was a mathematical construction, is in itself a major technical and theoretical step. More so, it expands our options for building real quantum computers, which will have a decisive impact in many areas, from cutting-edge medical research to cryptography and financial management.
[α] Fildes, J. (2009, July 15). Weaving the way to the Moon. BBC News. http://news.bbc.co.uk/1/hi/8148730.stm
[β] Visual Introduction to the Apollo Guidance Computer, Part 3: Making the Apollo Guidance Computer. AGC – Visual Introduction to the Apollo Guidance Computer, Part 3. http://authors.library.caltech.edu/5456/1/hrst.mit.edu/hrs/apollo/public/visual3.htm
[γ] Saida, D., Hidaka, M., Imafuku, K. and Yamanashi, Y. (2022). Quantum annealing factorization using superconducting flux qubits implementing a Hamiltonian multiplier. Scientific Reports, 12(1). https://doi.org/10.1038/s41598-022-17867-9
[δ] Andersen, TI, Lensky, YD, Kechedzhi, K., Drozdov, IK, Bengtsson, A., Hong, S., Morvan, A., Mi, X., Opremcak, A., Acharya, R., Allen, R . . ., Ansmann, M., Arute, F., Arya, K., Asfaw, A., Atalaya, J., Babbush, R., Bacon, D., Bardin, JC, … Roushan, P. (2023) . Non-abelian braiding of graph vertices in a superconducting processor. Nature. https://doi.org/10.1038/s41586-023-05954-4
[ε] Iqbal, M., Tantivasadakarn, N., Verresen, R., Campbell, SL, Dreiling, JM, Figgatt, C., Gaebler, JP, Johansen, J., Mills, M., Moses, SA, Pino, JM, Ransford, A., Rowe, M., Siegfried, P., Stutz, RP, Foss-Feig, M., Vishwanath, A., and Dreyer, H. (May 5, 2023). Creation of a non-abelian topological order and anyons on a trapped ion processor. arXiv.org. https://arxiv.org/abs/2305.03766
Hector-Xavier Delastik is Applied Physicist, YD Department of Medicine, University of Patras
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