We are in the middle of a quantum computing race. There are claims that it will be a game changer for data scientists, and that it will mean new algorithms and systems to extract knowledge from data.
Governments have jumped into the act. China’s investment in this technology is believed to be worth $10 billion, and the European Union has launched a €1 billion ($1.1 billion) quantum master plan.
In the United States, President Donald Trump signed the National Quantum Initiative Act in December 2018 to provide $1.2 billion to promote quantum information science over a five-year period.
But within the world of data scientists there is an ongoing debate regarding the future of this technology. After Galileo, let’s call the proponents of the two main opposing positions Simplicio the physicist and Salviati the engineer, with Sagredo as the neutral layperson who has interest in Mullah Nasruddin stories.
Simplicio: Quantum computing will be one of the key technologies that decide which nation gets to be the leading technological power of the 21st century. Quantum computers operate in a mode where several pieces of information are simultaneously processed, providing an advantage over current-day machines. When built, quantum machines will be faster than the most powerful classical supercomputers and thereby provide an edge in code-breaking and the solution of certain optimization problems.
Juggling Pins on Top of an Inverted Pyramid
Salviati: While the mathematics at the basis of quantum algorithms is fine, there are practical engineering reasons why such computers will never be built.
Unlike a classical computer that uses 0s and 1s (these could be charges or voltages on different points in a circuit), a quantum computer uses states that may be seen as waves together with their phases. Like waves, quantum bits (qubits) exist in superposition.
The quantum waves interact with the environment, and the computer can hopelessly decohere in a fraction of a second. And so the computation must be completed in very quick time, which places extreme constraints on the system. Without correction of random errors that are inevitable in any physical system, the results will be worthless.
The loading of the information on the quantum computer is like balancing an inverted pyramid (we may call it the initialization problem[i]), and this balancing is to be done with objects that are themselves flying about in all different directions. The juggler must then mount this pyramid and continue juggling the pins while ensuring he doesn’t fall down.
Sagredo: Believe in the future of technology. Remember Archimedes said, “Give me a lever and a place to stand, and I shall move the earth.”
Simplicio: NASA, Google, IBM, and other organizations are testing quantum computing systems with around 20 qubits. I know that we are far behind the milepost of 50 qubits that was set up by DARPA for 2012. But one must be patient.
Salviati: There is this assessment by Michel Dyakonov in IEEE Spectrum[ii]:
“There is a tremendous gap between the rudimentary but very hard experiments that have been carried out with a few qubits and the extremely developed quantum-computing theory, which relies on manipulating thousands to millions of qubits to calculate anything useful. That gap is not likely to be closed anytime soon.”
“Such a computer would have to be able to manipulate—on a microscopic level and with enormous precision—a physical system characterized by an unimaginably huge set of parameters, each of which can take on a continuous range of values. Could we ever learn to control the more than 10^300 continuously variable parameters defining the quantum state of such a system? My answer is simple. No, never.”
Sagredo: Once Mullah Nasruddin promised his king that he could teach his donkey to read. He said all that he needed was 1,000 dinars and 10 years. The king agreed but insisted that if the donkey failed the test, Nasruddin would be put to death. When he reached home with the money, his wife was furious. Relax, Nasruddin told his wife, 10 years is a long time. The king will be dead, the donkey will be dead, or he will be dead. In the worst case, they can flee the kingdom in the 10th year.
Simplicio: Look for the new unexpected research findings that will be obtained as a side result of the quantum computing initiative.
Simplicio: Quantum cryptography is a breakthrough technology. Two users can exchange keys without anyone being able to break the system. Surely, this is a fundamental advance of the greatest importance both for civilian communications and military applications[iii]. And isn’t it great that such key exchange can be done using wireless between satellites and with naval ships?
We must also design encryption systems that are resistant to compromise by quantum computers, if and when they are built. The government is investing resources into the development of new encryption schemes that are post-quantum.
Salviati: But quantum cryptography is used only for key distribution (QKD). First, the two parties must be authenticated, which can only be done classically because the world of conscious agents is classical[iv]. Since a chain is only as strong as its weakest link, there is no point doing QKD, for the authentication process itself can be used to exchange keys.
Simplicio: We cannot yield the leadership in this technology to competitors who don’t have commitment to democracy and open society.
Research on post-quantum encryption schemes will help us find new methods of data security that keep us ahead of our rivals.
Sagredo: One day Mullah Nasruddin was in a mischievous mood. He assembled a crowd, and told them a made-up story about gold in the abandoned house beyond the village. When everybody ran to get their hands on the gold, Nasruddin started running with them. When asked by his friends why he was doing so, he said "So many people believe it, that I think it may be true!"
Conclusion: The debate goes on. It is still time to watch from the sidelines.
[i] S. Kak, The initialization problem in quantum computing. Foundations of Physics 29: 267-279, 1999.
[ii] M. Dyakonov, The case against quantum computing. IEEE Spectrum. 15 November 2018.
[iv] S. Kak, Epistemic view of quantum communication. In Quantum Foundations, Probability and Information, A. Khrennikov and B. Toni (editors). Springer-Verlag International, pp. 119-128, 2018.