Quantum Supremacy: How the Quantum Computer Revolution Will Change Everything

by Michio Kaku

Quantum computers might usher in an entirely new age for the economy, society, and our way of life. But quantum computers are more than just another powerful computer. They are a new type of computer that can tackle problems that digital computers can never solve, even with an infinite amount of time. For example, digital computers can never accurately calculate how atoms combine to create crucial chemical reactions, especially those that make life possible. Digital computers can only compute on digital tape, consisting of a series of 0s and 1s, which are too crude to describe the delicate waves of electrons dancing deep inside a molecule. For example, when tediously computing the paths taken by a mouse in a maze, a digital computer has to painfully analyze each possible path, one after the other. A quantum computer, however, simultaneously analyzes all possible paths at the same time, with lightning speed.

The tremors caused by these remarkable achievements have also shaken boardrooms and top secret intelligence agencies around the world. Documents leaked by whistleblowers have shown that the CIA and the National Security Agency are closely following developments in the field. This is because quantum computers are so powerful that, in principle, they could break all known cybercodes. This means that the secrets carefully guarded by governments, which are their crown jewels containing their most sensitive information, are vulnerable to attack, as are the best-kept secrets of corporations and even individuals. This situation is so urgent that even the U.S. National Institute of Standards and Technology (NIST), which sets national policy and standards, recently issued guidelines to help large corporations and agencies plan for the inevitable transition to this new era. NIST has already announced they expect that by 2029 quantum computers will be able to break 128-bit AES encryption, the code used by many companies.

The rise of quantum computers is a sign that the Age of Silicon is gradually coming to a close. For the past half-century, the explosion of computer power has been described by Moore’s law, named after Intel founder Gordon Moore. Moore’s law states that computer power doubles every eighteen months. This deceptively simple law has tracked the remarkable exponential increase in computer power, which is unprecedented in human history. There is no other invention which has had such a pervasive impact in such a brief period of time.

Atoms are like spinning tops. In a magnetic field, they can align either up or down with respect to the magnetic field, which can correspond to a 0 or a 1. The power of a digital computer is related to the number of states (the 0s or 1s) you have in your computer. But due to the weird rules of the subatomic world, atoms can also spin in any combination of the two. For example, you can have a state in which the atom spins up 10 percent of the time and spins down 90 percent of the time. Or it spins up 65 percent of the time and spins down 35 percent of the time. In fact, there are an infinite number of ways that you can have an atom spin. This vastly increases the number of states that are possible. So the atom can carry much more information, not just in a bit, but a qubit, i.e., a simultaneous mixture of the up and down states. Digital bits can only carry one bit of information at a time, which limits their power, but qubits, or quantum bits, have almost unlimited power. The fact that, at the atomic level, objects can exist simultaneously in multiple states is called superposition. (This also means the familiar laws of common sense are routinely violated at the atomic level. At that scale, electrons can be in two places at the same time, which is not true for large objects.) In addition, these qubits can interact with each other, which is not possible for ordinary bits. This is called entanglement. Whereas digital bits have independent states, each time you add another qub...

The problem facing quantum computers was also foreseen by Richard Feynman when he first proposed the concept. In order for quantum computers to work, atoms have to be arranged precisely so that they vibrate in unison. This is called coherence. But atoms are incredibly small and sensitive objects. The smallest impurity or disturbance from the outside world can cause this array of atoms to fall out of coherence, ruining the entire calculation. This fragility is the main problem facing quantum computers. So the trillion-dollar question is: Can we control decoherence? In order to minimize the contamination coming from the outside world, scientists use special equipment to drop the temperature to near absolute zero, where unwanted vibrations are at a minimum. But this requires expensive, special pumps and tubing to reach those temperatures. But we are faced with a mystery. Mother Nature uses quantum mechanics at room temperature without a problem. For example, the miracle of photosynthesis, one of the most important processes on earth, is a quantum process, yet it takes place at normal temperatures. Mother Nature does not use a roomful of exotic devices operating at near absolute zero to execute photosynthesis. For reasons that are not well understood, in the natural world coherence can be maintained even on a warm, sunny day, when disturbances from the outside world should create chaos at the atomic level. If we could one day figure out how Mother Nature performs her magic at ...

There are many areas where quantum computers can overtake conventional digital computers: 1. Search engines

2. Optimization

3. Simulation

4. Merger of AI and Quantum Computers

Jeremy O’Brien, founder of PsiQuantum, emphasizes that this revolution is not about building faster computers. Instead, it’s about tackling problems, like complex chemical and biological reactions, that no conventional computer could solve no matter how much time we gave it. He says, “We’re not talking about doing things faster or better…we’re talking about being able to do these things at all….These problems are forever beyond the reach of any conventional computer that we could ever build…even if we took every silicon atom on the planet and turned it into a supercomputer, we still could not solve these…hard problems.”

At its most fundamental level, all life is quantum mechanical, and so beyond the reach of digital computers. But quantum computers will lead the way into the next stage, when we decipher the mechanisms at the molecular level that tell us how they work, allowing scientists to create new genetic pathways, new therapies, new cures to conquer previously incurable diseases.

Quantum computers are already being connected to neural networks, to create the next generation of learning machines that can literally reinvent themselves. The laptop sitting on your desk, by contrast, never learns. It is no more powerful today than it was last year. Only recently, with new advances in deep learning, are computers taking the first steps to recognizing mistakes and learning. Quantum computers could exponentially accelerate this process and have singular impacts on medicine and biology.

Instead of building increasingly complex adding machines like Babbage’s difference engine, Alan Turing eventually asked himself a different question: Is there a mathematical limit to what a mechanical computer can perform? In other words, can a computer prove everything?

Turing began by defining what is computable. He said, in essence, that a theorem is computable if it can be proven in a finite amount of time by a Turing machine. If a theorem requires an infinite amount of time on a Turing machine, then, for all intents and purposes, the theorem is not computable, and we don’t know if the theorem is correct or not. Therefore, it would not be provable. Simply put, Turing then expressed the question raised by Gödel in a concise form: Are there true statements that cannot be computed in a finite amount of time by a Turing machine, given a set of axioms? Like the work of Gödel, Turing showed that the answer is yes. Once again, this shattered the ancient dream of proving the completeness of mathematics, but in a way that was intuitive and simple. It meant that, even with the most powerful computer in the world, one can never prove all true statements in mathematics in a finite amount of time with a given set of axioms.

Turing and his colleagues set upon this crucial problem by designing calculating machines that might systematically crack these impenetrable codes. Their first breakthrough, called the bombe, resembled Babbage’s difference engine in some ways. Instead of steam-driven mechanisms like previous machines, whose gears and cogs were slow, difficult to make, and often jammed, the bombe relied on rotors, drums, and relays, all powered by electricity. But Turing was also involved with another project, Colossus, with an even more ingenious design. Historians believe it was the world’s first programmable digital electronic computer. Instead of mechanical parts like the difference engine or the bombe, they used vacuum tubes, which can send electrical signals near the speed of light. Vacuum tubes can be compared to valves controlling the flow of water. By turning a small valve, one can shut off the water flowing in a much larger pipe, or let it flow unimpeded. This, in turn, can represent the number 0 or 1. So a system of water pipes and valves can represent a digital computer, where the water is like the flow of electricity. In the machines at Bletchley Park, a large array of vacuum tubes could perform digital calculations at enormous speeds by turning the flow of electricity on or off in the vacuum tubes. Thus, the work of Turing and others replaced the analog computer with a digital computer. One version of Colossus contained 2,400 vacuum tubes and filled up an entire room.

Historians such as Harry Hinsley have estimated that the work of Turing and others at Bletchley Park shortened the length of war by about two years and saved over 14 million lives.

After the war, Turing returned to an age-old problem that had intrigued him as a youth: artificial intelligence. In 1950, he opened his landmark paper on the subject by stating, “I propose to consider the question: Can machines think?” Or to put it another way, is the brain a Turing machine of some sort? He was tired of all the philosophical discussions that stretched back centuries about the meaning of consciousness, the soul, and what makes us human. Ultimately, all this discussion was pointless, he thought, because there was no definitive test or benchmark for consciousness. So Turing came up with the celebrated Turing test. Put a human in a sealed room and a robot in another room. You are allowed to ask each one any written question and read their responses. The challenge is: Can you determine which room held the human? He called this test the imitation game. In his paper, he wrote, “I believe that in about fifty years’ time, it will be possible to programme computers, with a storage capacity of about 109, to make them play the imitation game so well that an average interrogator will not have more than 70 percent chance of making the right identification after five minutes of questioning.” The Turing test replaces endless philosophical debate with a simple reproducible test, to which there is a simple yes-or-no answer. Unlike a philosophical question, for which there is often no answer, this test is decidable. Furthermore, it sidesteps the slippery question of “thinkin...

In 1952, someone burglarized Turing’s home. When the police came to investigate, they found evidence that Turing was gay. For this, he was arrested and sentenced under the Criminal Law Amendment Act of 1885. The punishment was quite harsh. He was given a choice of going to prison or undergoing a hormonal procedure. When he chose the latter, he was given stilboestrol, a synthetic form of the female sex hormone estrogen, which caused him to grow breasts and become impotent. The controversial treatments lasted for one year. Then one day, he was found dead in his home. He died from a fatal dose of cyanide poison. It was reported that next to him there was a half-eaten poison apple, which some speculated was how he committed suicide. It is a tragedy that one of the creators of the computer revolution, who helped save the lives of millions and defeat fascism, was in some sense destroyed by his own country.

According to Newton, the universe was a clock. It was ticking away following his three laws of motion in a precise and predetermined way. This was called Newtonian determinism, which held sway for several centuries. (It is sometimes called classical physics, to distinguish it from quantum physics.)

Ancient artisans knew that if clay were heated up to high enough temperature in a furnace, it would eventually glow brightly. It would start becoming red hot, then yellow hot, and finally bluish-white hot. We see this every time we light up a match. At the top of the flame, where it is coolest, the flame is red. In the center, the flame is yellow. And, if the conditions are right, the bottom of the flame is blue-white hot. Physicists tried to derive this well-known property of hot objects and failed miserably. They knew that heat is nothing but atoms in motion. The greater the temperature of an object, the faster its atoms move. They also knew that atoms have electrical charges as well. If you move a charged atom fast enough, it radiates electromagnetic radiation (like radio or light), according to the laws of James Clerk Maxwell. The color of a hot object indicates the frequency of the radiation. So, using Newton’s theory applied to the atom, and using Maxwell’s theory of light, one can calculate the light emitted from a hot object. So far, so good. But when the calculation is actually performed, disaster strikes. One finds that the energy emitted can become infinite at high frequencies, which is impossible. This was called the Rayleigh-Jeans catastrophe. It showed physicists that there was a gaping hole in Newtonian mechanics. One day, Planck tried to derive the Rayleigh-Jeans catastrophe for his physics class, but with a strange, novel method. He was tired of doing it i...

Although his theory indisputably fit the experimental data and opened up an entirely new branch of physics, he was hounded for years by stubborn, die-hard believers in the classical, Newtonian idea. Describing this blizzard of opposition, Planck wrote: “A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”

By comparing the resonances predicted by Schrödinger’s waves with actual elements, one found a remarkable one-to-one correspondence. Physicists, who for decades were stumped trying to understand the atom, were now able to peek inside the atom itself. When one compared these wave patterns to the hundred or so chemical elements found in nature by Dmitri Mendeleev and others, one could explain the chemical properties of the elements using pure mathematics. This was a staggering achievement. Physicist Paul Dirac would write prophetically: “The fundamental laws necessary for the mathematical treatment of a large part of physics and the whole of chemistry are thus completely known, and the difficulty lies only in the fact that application of these laws leads to equations that are too complex to be solved.”

As spectacular and powerful as the Schrödinger equation was, there was still one important, but embarrassing, question. If the electron was a wave, then what is waving? The solution would divide the physics community right down the middle, pitting physicists against one another for decades to come. It would spark one of the most controversial debates in the entire history of science, challenging our very notion of existence. Even today, there are conferences debating all the mathematical nuances and philosophical implications of this split. And one by-product of this debate, as it would turn out, is the quantum computer. Physicist Max Born lit the fuse of this explosion by postulating that matter consists of particles, but the probability of finding that particle is given by a wave. This immediately cleaved the physics community in two, with the founders of the “old” guard on one side (including Planck, Einstein, de Broglie, and Schrödinger, all denouncing this new interpretation), and Werner Heisenberg and Niels Bohr on the other, creating the Copenhagen school of quantum mechanics. This new interpretation was too much, even for Einstein. It meant that you can only calculate probabilities, never certainties. You never knew precisely where a particle was; you could only calculate the likelihood that it was there. In some sense, electrons can be two places at the same time. Werner Heisenberg, who came up with an alternative but equivalent formulation of quantum mechanics, w...

But the most crucial and outrageous statement is number four, which holds that only after a measurement is made will the wave finally “collapse” and yield the correct answer, giving the probability of finding the electron in that state. One cannot know which state the electron is in until a measurement is made. This is called the measurement problem. To refute the last statement, Einstein would say, “God does not play dice with the universe.” But according to legend, Niels Bohr fired back, “Stop telling God what to do.” It is precisely postulates 3 and 4 that make quantum computers possible. The electron is now described as the simultaneous sum over different quantum states, which gives quantum computers their calculational power. While classical computers only sum over just 0s and 1s, quantum computers sum over all quantum states Ψn(x) between 0 and 1, which vastly increases the number of states and therefore their range and power.

Three physicists won the Nobel Prize in 1956 for the creation of this wonder device: Bell Laboratories scientists John Bardeen, Walter Brattain, and William Shockley. Today, a replica of the world’s first transistor is on display in a glass case in the Smithsonian Museum in Washington. It is a crude, awkward-looking device, but delegations of scientists from around the world are known to approach this transistor with silent reverence, and some even bow in front of it, as if it were some deity. Bardeen, Brattain, and Shockley used a new quantum form of matter, called the semiconductor. (Metals are conductors, which allow for the free flow of electrons. Insulators, like glass, plastic, or rubber, do not conduct electricity. Semiconductors are in between and can both carry and stop the flow of electrons.) The transistor exploits this crucial property. It is the successor to the old vacuum tube that was ingeniously used by Turing and others.

In 1981, Feynman emphasized that only a quantum computer can truly simulate a quantum process. But Feynman did not elaborate on precisely how a quantum computer might be built. The next person who picked up the torch was David Deutsch of Oxford University. Among other achievements, he was able to answer the question: Can you apply quantum mechanics to a Turing machine? Feynman had hinted at this problem, but never wrote down the equations for a quantum Turing machine. Deutsch went on to fill in all the details. He even designed an algorithm that could run on this hypothetical quantum Turing machine. A Turing machine, as we have seen, is a simple classical device, based on a processor, that turns the number on an infinitely long tape into another number and therefore performs a series of mathematical operations. The beauty of a Turing machine is that it summarizes all the properties of a digital computer in a simple, compact form, which can then be rigorously studied by mathematicians. The next step is to add the quantum theory to Turing’s invention, which would allow scientists to study the bizarre properties of quantum computers in a rigorous way. In a quantum Turing machine, thought Deutsch, one replaces a classical bit with a quantum qubit. This introduces several important changes. First, the basic manipulations of the Turing machine (e.g., replacing a 0 with a 1 and vice versa, and moving the tape forward or backward) remain roughly the same. But the bits are radicall...

Thus, parallel universes necessarily emerge when you try to describe the entire universe in quantum terms. Instead of parallel electrons, now we have parallel universes. But this leaves open the next question: Can we visit these parallel universes? Why don’t we see this infinite collection of parallel universes, some of which might resemble our own, while others might be bizarre and preposterous?

Let’s now summarize all the bizarre features of the quantum theory that make quantum computers possible. 1. Superposition. Before you observe an object, it exists in many possible states. So an electron can be in two places at the same time. This vastly increases the power of a computer, since you have more states to calculate with. 2. Entanglement. When two particles are coherent and you separate them, they can still influence each other. This interaction takes place instantly. This allows atoms to communicate with each other, even when separated. This means that computer power grows exponentially as more and more qubits are added that can interact with each other, far faster than ordinary computers. 3. Sum over paths. When a particle moves between two points, it sums over all possible paths connecting these two points. The most likely path is the classical, nonquantum path, but all these other paths also contribute to the final quantum path of the particle. This means that even paths which are extremely unlikely may become real. Perhaps the paths of molecules that created life became real because of this effect, making life possible. 4. Tunneling. When faced with a large energy barrier, normally a particle fails to penetrate it. But in quantum mechanics, there is a small but finite probability that you can “tunnel” or penetrate through the barrier. This might be why the complex chemical reactions of life can proceed at room temperature, even without vast amounts of energy.

The leading code for secret transmissions is called the RSA standard and is based on factoring a very large number. For example, start with two numbers, each 100 digits long. If you multiply them together, you can get a number approaching 200 digits. Multiplying two numbers is an easy task. But if someone gave you this 200-digit number to start with, and asked you to factorize it (find the two numbers that multiply together to make it), it might take centuries or more to do this with a digital computer. This is called a trapdoor function. In one direction, when multiplying two numbers, the trapdoor function is trivial. But in the other direction, it’s very difficult. Both classical and quantum computers can factorize a large number. In fact, a classical computer can, in principle, compute anything that a quantum computer can compute, and vice versa, but if the data is too complex it can overwhelm classical computers. The key advantage of a quantum computer is time. Although both classical and quantum computers can perform certain tasks, the time it takes classical computers to crack a difficult problem may make it totally impractical. So the time it takes for a classical computer to factorize a large number is prohibitively large, making it impractical to break into our secrets. But a quantum computer can crack the code after a given amount of time, which is still large but maybe just small enough to be practical.

In the future, top secret messages may be sent on a separate internet channel carried by laser beams, not electrical cables. Laser beams are polarized, meaning that the waves vibrate in only one plane. When a criminal tries to tap into the laser beam, this changes the direction of polarization of the laser, which is immediately detected by a monitor. In this way, you know, by the laws of the quantum theory, that someone has tapped into your communication.

This might mean that, in the future, there could be two layers to the internet. Some organizations, like banks, large corporations, and governments, may pay a premium to send messages on a laser-based internet, which is guaranteed to be secure, while everyone else will use the ordinary internet, which does not have this extra costly layer of protection. This problem of security is also leading to a new technology called quantum key distribution (QKD), which transfers encryption keys using entangled qubits, so that one can detect immediately if someone is hacking into your network. Already, Japan’s Toshiba company has predicted that QKD may generate up to $3 billion in revenue by the end of this decade.

Basically, any quantum system that can superimpose states of 0s and 1s and entangle them so that they can process this information can become a quantum computer. Electrons and ions that spin up or down could serve this purpose, or polarized photons that spin clockwise or counterclockwise. Since the quantum theory governs all matter and energy in the universe, there are potentially thousands of ways to build a quantum computer. In a lazy afternoon, a physicist may dream up scores of ways of representing the superposition of 0s and 1s to create an entirely new quantum computer.

But if cancer is so deadly, then why didn’t evolution get rid of these defective genes millions of years ago by natural selection? The answer is that cancer mainly spreads after our reproductive years are over, so there is less evolutionary pressure to eliminate cancer genes.

Biologist Richard Peto of Oxford noticed something odd about elephants. Because of their massive size, one would expect that they would have more cancers than much smaller animals. After all, a larger mass means more cells are constantly dividing and introducing the possibility for genetic errors, like cancer. But surprisingly enough, elephants have a relatively low cancer rate. This became known as Peto’s paradox.

In nature, Brooks realized, animals are not programmed to walk from the start. They learn the hard way, by putting one leg in front of the other, falling down, and doing it again. Trial and error is the way of nature. This goes back to the advice every music teacher gives to their promising student. How do you get to Carnegie Hall? Answer: practice, practice, practice. In other words, Mother Nature designs creatures that are pattern-seeking learning machines, using trial and error to navigate the world. They make mistakes, but with each iteration, they come closer to success. This is a bottom-up approach, and it starts with nothing but bumping into things. For example, babies learn by mimicking adults. If you put a tape recorder in a crib at night, you will hear babies babble constantly. What they are actually doing is endlessly practicing making the sounds they hear over and over again, until they can duplicate them correctly.

The only proven way in which to lengthen the life span of an animal is through caloric restriction. In other words, if you eat 30 percent fewer calories, you can live roughly 30 percent longer, depending on the animal being studied.

The biggest solar flare in recorded history, called the Carrington Event, took place in 1859. Back then, this monster solar flare caused telegraph wires to catch on fire over much of Europe and North America. It created atmospheric disturbances all over the planet, with the aurora borealis blanketing the night sky over Cuba, Mexico, Hawaii, Japan, and China. You could read the newspaper at night in the Caribbean by the light of the aurora. In Baltimore the aurora was brighter than a full moon.

The Carrington Event happened when the Electric Age was in its infancy. Since then, there have been attempts to reconstruct the data and then estimate what might occur if another Carrington Event were to happen in modern times. In 2013, researchers at Lloyd’s of London and Atmospheric and Environmental Research (AER) in the U.S. concluded that another Carrington Event could cause up to $2.6 trillion in damages. Modern civilization could come to a grinding halt. It would knock out our satellites and the internet, cause short circuits in power lines, paralyze all financial communications, and cause global blackouts. We would be thrown perhaps 150 years into the past. Rescue and repair teams would fail to come to the rescue, because they too would be caught in the global blackout. With perishable food rotting, eventually this could trigger massive food riots and a disintegration of social order and even governments, as people desperately scavenge for scraps of food.