Dr. Michio Kaku, the famous theoretical physicist, walks us through the evolutionary journey of computing, from analog to digital to the quantum era.

Quantum computers hold enormous promise because of their ability to exploit the weirdness of quantum mechanics. If nature gives us full access to its secrets, we could increase computing power exponentially, which in turn would allow us to solve all types of complex problems.

The race between major technology companies to create a quantum computer is intense, but the endeavor faces manychallenges. For example, we have yet to create a fully functional quantum computer.

**MICHIO KAKU:**We all know that digital computers changed almost every aspect of our lives. Well, the arrival of quantum computers could be even more historic than that. We are now in the initial stages of the next revolution. We are talking about a new generation of computers: the ultimate computer, a computer that calculates on atoms, the ultimate constituents of matter itself.

The question is: Who is involved in this race to perfect quantum computers? And the answer is: everyone. All the big players are part of this race, because if they're not, Silicon Valley could become the next Rust Belt. Anyone interested in security is also interested in quantum computing. They can crack almost any code based on digital technology. This is why the FBI, CIA and all national governments are following this very closely.

Quantum computers will change everything, the economy, how we solve problems, the way we interact with the universe. You name it, quantum computers will be there. I am Dr. Michio Kaku, professor of theoretical physics at the City University of New York and author of "Quantum Supremacy," about the rise of quantum computers.

You see, computers have gone through three basic stages: Stage one was the analog computer. So 2,000 years ago there was a shipwreck and in the boat that sank there was an apparatus and as you brushed away the dirt and grime you began to realize that it was a machine, a machine of incredible complexity. It was actually the world's first analog computer, and it was designed to map the motion of the Moon, Sun, and planets to simulate the universe.

But as we primitive people became more prosperous, we had to count things - count how many cows you had, count how much profit you made. Analog computers could be based on sticks, bones, whatever was needed to count. So this went on for thousands of years until we finally reached the work of Charles Babbage. He creates the ultimate analog computer with hundreds of gears and levers and pulleys. And by turning the hand crank, you could then calculate longitude, latitude, you could calculate interest. It was very valuable to have an instrument like that for the banking sector, for trade.

Then comes World War II. Babbage's machine is simply too primitive to break the German code, so the job was given to mathematicians like Alan Turing. Alan Turing was the one who codified many of the laws of computation into what is called, and of course, digital. Now the digital revolution is based on transistors. It works on zeros and ones, zeros and ones with the speed of electricity. Any digital computer is a Turing machine.

The next step beyond digital computers is the quantum era. Richard Feynman was one of the founders of quantum electrodynamics, but also a visionary. And he asked himself a simple question: How small can you make a transistor? And he realized that the ultimate transistor is an atom, an atom that could control the flow of electricity, not just on or off, but everything in between.

We have to go to quantum computers, computers that compute on atoms instead of transistors. Transistors are based on zeros and ones, zeros and ones. The reality is not. Reality is based on electrons and particles, and these particles in turn act as waves. So you need a new set of math to discuss the waves that make up a molecule, and that's where quantum computers come in.

They are based on electrons, and these electrons, why do they have so much computing power? Because they could be in two places at the same time - that's what gives quantum computers their power. They calculate not just one universe, but an infinite number of parallel universes. At the fundamental level, quantum mechanics can be reduced to a cat, Schrodinger's cat.

Let's take a box. A cat is placed in the box, and the question is: Is the cat dead or alive? Well, until you open the box, you don't know. It is alive and dead at the same time. It is in a superposition of two states. In other words, the universe is split in two. In one half, the cat is alive. In the other universe, the cat is dead. It is the basis of quantum theory that until you make a measurement, the cat can exist in both states simultaneously, in fact in any number of states simultaneously.

The cat can be dead, alive, playing, jumping, sideways, sick, any number of states. Now, why do I mention this? Because this sums up the power of quantum computing. Quantum computers compute on parallel universes. That is why they are so strong. So how much faster is a quantum computer compared to a digital computer? In principle, when we talk about digital computers, we can measure their power in terms of bits.

For example, spin up, spin down, zeros and ones will make up a bit. For a large digital computer, we're now talking about billions of bits modeled by transistors, except now, quantum computers aren't just talking about spin up or spin down, but everything in between - that's called a qubit. A qubit represents all the possibilities of an object spinning between up and down.

Thousands of qubits can now be modeled with the latest generation of quantum computers. Eventually we hope to hit a million. And then we talk about exceeding the power of ordinary digital computers. This is the point where a quantum computer can surpass and outperform a digital computer on a particular task. We passed that several years ago, but we want a machine that can exceed the power of any digital computer. We're not there yet, but we're very close.

The biggest problem facing quantum computers is the issue of 'decoherence'. Everything is based on particles like electrons, and electrons have waves associated with them. When these waves vibrate in unison, it is called 'coherence', and then you can do calculations of a quantum mechanical nature. But if you fall out of context, then everything vibrates at a different frequency. And what is it called? Noise.

You have to reduce the temperature down to almost absolute zero so that everything vibrates basically slowly in unison - it's hard. Now nature solves this problem: it is the basis of all life on earth. Photosynthesis, for example, is a quantum mechanical process. Mother Nature can create consistency at room temperature. Amazing. Mother Nature is still smarter than us when it comes to quantum theory.

So let's face it. There are obstacles affecting the growth of quantum computers, but they pale in comparison to the benefits that quantum computers can unleash. We are talking about opening the floodgates. For example, take a look at the food supply. The 'green revolution' that allows us to feed the world's population is slowly coming to an end. We are trying to use quantum computers to unlock the secret of how to make fertilizer from nitrogen.

Take a look at energy. Quantum computers may be able to create fusion power by stabilizing the super-hot hydrogen inside a fusion reactor. And take a look at medicine. You realize that life is based on molecules, molecules that can create Alzheimer's disease, Parkinson's disease, cancer. These diseases are beyondreach of digital computers. But hey, that's what quantum computers do.

We will be able to model diseases at the molecular level, which is why we hope to cure the incurable using quantum computers. We are talking about turning medicine on its head. My personal hope for quantum computers is that we will be able to create a theory of the entire universe, the theory that eluded Einstein, the theory that would explain black holes and supernovae and galactic evolution. But the equations are so complex that no one, no one has been able to solve them. Perhaps they will be solved in the memory of a quantum computer.