Factoring large numbers is, of course, the intentionally hard problem at the core of public-key cryptography (PKC) as implemented in the RSA algorithm, the kind of cryptography that is the basis of almost all communications today over the internet. This includes securely sending credit card numbers, bank payments and ensuring the security of online messaging systems. RSA-based cryptography depends on the one-way hardness of the factoring of large numbers into two prime factors. Producing the large number is easy; we just multiply the two factors. Given an arbitrarily large number, however, it is exponentially difficult to find its two prime factors.
Shor realized that we can use a quantum computer to solve another problem that is equivalent to the RSA factoring problem; the factoring problem is, in fact, equivalent to the period-finding problem which another researcher, Daniel Simon, had already shown could be tackled by a quantum computer. From this early work, it became clear that quantum technologies would one day change the world.
So what we can expect in the future from quantum technologies and where should investors and businesses start to focus in this field?
Quantum sensing: There are dozens of startups now exploring different quantum sensing techniques. For example, QuSpin, Inc. is a startup that has developed a quantum sensor for minute changes in magnetic fields. The University of Nottingham is using this QuSpin sensor to built a prototype of a brain scanner. Since the brain has both electrical signals and a magnetic signal, we can use these detectors to image brain function in real time; this data is complementary to an EEG which detects the electrical signal of brain activity. There are also startups using quantum sensing for navigation. AO Sense, Inc., for example, is a company that has developed technology to provide precise navigation, even when there is no GPS or other external signals!
Quantum Communications and Cybersecurity: a growing number of companies and governments are investing in this field. Companies such as ID Quantique are producing small chips for mobile phones to provide more secure communications based on quantum random number generation. Other startups are focusing on algorithms for post-quantum cryptography.
Quantum computing: There are three major areas of investment in quantum computing:
Computing platforms: these are startups that are building quantum computers and hope to scale to a fault-tolerant device one day. There are several approaches to building these computers including trapped ions, superconducting qubits, photonics, and others. Each of these efforts will require hundreds of millions of dollars of capital and years of further development.
Quantum computing control tools: These are companies that enable the builders of quantum computers to gain more precise control over the qubits in their machines. Two examples in this space are Q-CTRL and Quantum Machines, Inc.
Quantum Computing Software: These will be the more numerous type of quantum computing startup since the startup capital required is much lower than the hardware companies. Examples of VC-backed companies in this sector are Zapata, QCWare and 1Qbit.
In summary, while these are early days in quantum technologies, it is clear that this field will have a significant impact on a wide range of economic sectors. While many have focused only on quantum computing, we encourage the reader to explore other quantum technologies such as quantum sensing and communications as well. Each of these areas will synergize with the others to bring about wave after wave of science and technology breakthroughs. Welcome to your quantum future.
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