Model of the inside of a quantum computer Bild: Bastian Benrath
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.
We are entering a new era which will catalyze discoveries in science and technology. Novel computing platforms will probe the fundamental laws of our universe and aid in solving hard problems that affect all of us. Machine learning programs powered by specialized chips are already yielding breakthrough after breakthrough.
Quantum computing is part of the larger field of quantum information science (QIS). All three branches of QIS – computation, communication, and sensing – are advancing at rapid rates and a discovery in one area can spur progress in another.
Businesses and investors are now ramping up their interest in these fields. In this piece, we will first outline the various quantum technologies and then cover opportunities and impact. While these are early days in quantum tech, we can see exciting possibilities coming down the road. In the past three years alone, funds invested more than $650 million into quantum tech companies. The quantum tech ecosystem is growing rapidly in many geographies across the globe and is not dominated by just one or two locations.
Quantum communication leverages the unusual properties of quantum systems to transmit information in a manner that no eavesdropper can read. This field is becoming increasingly critical as quantum computing drives us to a post-quantum cryptography regime: quantum computers of sufficient size will be able to break many cryptographic schemes currently in use, which means that new protocols will need to be developed and put into use.
An emerging class of sensors
There are quantum-resistant schemes currently being tested – for example, as part of the NIST process – for which there are no known quantum (or classical, for that matter) attacks. For ultimate security, however, it may be that some will choose to rely on new quantum communication protocols that make use of a new quantum internet. Those protocols will be guaranteed secure by the fundamental laws of physics, but will require new hardware beyond what we currently use for classical data transmission.
Quantum sensing is a robust field of research that uses quantum devices to move beyond classical limits in sensing magnetic and other fields. For example, there is an emerging class of sensors for detecting position, navigation, and timing (PNT) at the atomic scale. These micro-PNT devices can provide highly accurate positioning data when GPS is jammed or unavailable.
Quantum sensors also show promise in the life sciences. Researchers have already demonstrated the use of nanoscale quantum sensors to measure the electromagnetic activity of single cells. We can use these sensors to monitor the firing of neurons and cardiac cells. These technologies can develop into cornerstone diagnostic and therapeutic devices in the future.
The trick is to build such a system
One of the critical differences between quantum and classical computation is that in quantum computing we are manipulating quantum states themselves; this gives us a much larger computing space to work in than in classical computers. In classical computers, if we wish to model a real-world quantum physical we can only do so with representations of such a system and we cannot implement the physics itself. This key difference leads to exciting possibilities for the future of computing and science. All this starts with fundamental truths about our world that were developed during the quantum mechanics revolution in the first half of the 20th century
So what exactly is a quantum computer? The answer to this question encompasses quantum mechanics (QM), quantum information theory (QIT) and computer science (CS). For our purposes, we will focus on the core of what makes a quantum computer distinct from classical computers: „A quantum computer is a device that leverages specific properties described by quantum mechanics to perform computation. Quantum computers use quantum bits -- qubits -- instead of classical bits for computation.“
More concretely, to build a quantum computer we need a series of qubits each of which is able to be in state 0 or 1 (just like a classical bit), but also in a linear combination of 0 and 1. In fact, there is an infinite number of such linear combinations; so a qubit has far more representational power than a classical bit. In fact, just 55 or so of these qubits can perform certain calculations that even a computer with billions of traditional bits could not accomplish in a short amount of time.
The possibility that we can leverage quantum mechanics to compute in new and interesting ways has been hiding in plain sight since the field’s early days; the principles of superposition and entanglement can form the basis of a very powerful form of computation. The trick is to build such a system that we can easily manipulate and measure.
Benioff demonstrated the theoretical basis
While Richard Feynman is often credited with the conception of quantum computers, there were several researchers who anticipated this idea. In 1979, Paul Benioff, a young physicist at Argonne National Labs, submitted a paper entitled “The computer as a physical system: A microscopic quantum mechanical Hamiltonian model of computers as represented by Turing machines”. In this paper, Benioff demonstrated the theoretical basis for quantum computing and then suggested that such a computer could be built. Yuri Manin also laid out the core idea of quantum computing in his 1980 book Computable and Non-Computable. The book was written in Russian, however, and only translated years later.
In 1981, Feynman gave a lecture entitled “Simulating Physics with Computers”. In this talk, he argued that a classical system could not adequately represent a quantum mechanical system: „...nature isn’t classical, dammit, and if you want to make a simulation of nature, you’d better make it quantum mechanical, and by golly it’s a wonderful problem, because it doesn’t look so easy…“
He then set out the features that a quantum computer should have to be useful. At the time of this lecture, however, it was unclear to Feynman and the physics community how one could build such a machine. Once Benioff, Manin and Feynman opened the doors, researchers began to investigate the nature of the algorithms that could be run on QCs. David Deutsch, a physicist at Oxford, suggested a more comprehensive framework for quantum computing in his 1985 paper. In this work, he describes in detail what a quantum algorithm would look like and anticipates that “one day it will become technologically possible to build quantum computers.”
Deutsch then went on to develop an example of an algorithm that would run faster on a quantum computer. He then further generalized this algorithm in collaboration with Richard Jozsa. This Deutsch-Jozsa algorithm made it clear that one day quantum computers would outpace even the biggest classical computers.
Now Peter Shor enters the scene. In 1994, Shor was a researcher in the mathematical division of Bell Labs. Shor studied the work of Deutsch, Jozsa, and others and realized he could construct an algorithm for factoring large numbers into two prime factors; factoring large numbers is believed to be intractable on a classical computer, but Shor’s factoring algorithm runs quickly on a quantum computer.
What can we expect?
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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