Name: Nature may have already solved the problem stumping quantum physicists | Jim Al-Khalili
Uploaded: 2026-03-10T18:10:55.000Z
Duration: 13 min 58 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

My name is Jamal Khalili and I'm Emeritus professor of Physics at the University of Surrey.

My book is called On Time, the Physics that Makes the Universe Tick.

Here we are a quarter of the way through the 21st century and celebrating the most, in my view, powerful and successful scientific theory we have ever come up with, quantum mechanics.

Quantum mechanics was developed in the early decades of the 20th century and describes the way atoms and the particles that make up atoms, the tiniest building blocks of matter, how they behave.

And they behave in a way very different from the way our everyday world behaves.

Quantum mechanics, as opposed to Newton's mechanics and Newton's laws of motion.

So in the quantum world, things are fuzzy, they're probabilistic.

An electron can be in more than one state at the same time.

Particles can move in multiple directions at the same time.

They can quantum tunnel through energy barriers like a ghost passing through a solid wall.

Things that we'd never see in our everyday world.

And yet that reality down at the quantum realm is our true reality.

Our whole universe ultimately behaves in a quantum way.

Now, the early discoveries of quantum mechanics led throughout the 20th century to all sorts of technologies, what we now call the first quantum revolution.

So the laser, the transistor, LEDs, the integrated circuits, the microchip, the computer, GPS smartphones, the Internet.

Almost all of our modern technology that we use today that relies on electronics is thanks to developing quantum mechanics.

Today we're on the threshold of a second quantum revolution, a revolution in technology based on even more counterintuitive ideas of quantum mechanics, things like quantum entanglement and quantum superposition.

So many people may have heard of quantum superposition in the context of the so called two slit experiment, where you send particles through a screen with two slits and it forms an interference pattern at the back.

Somehow the particle goes through both slits simultaneously and behaves like a wave.

This is the notion that even Einstein famously didn't like when he first encountered it, that two separated particles can somehow be instantaneously in communication with each other.

Their fates are intertwined because they have to be described by the same single quantum state, however far apart they are.

Well, we're now using superposition and entanglement to develop whole new technologies.

Some are coming, they will be with us maybe in a decade or two, like the quantum computer.

So we are now developing instruments that carry out what's called quantum sensing.

We have even developed this way of sensing Very weak magnetic fields.

You wear a helmet, like a cycling helmet on your head.

And thanks to quantum entanglement, we can measure single the firing of single neurons.

So essentially reading people's brainwaves.

One other technology that's being developed at the moment Is quantum communication.

Now we know the way the Internet is connected up through optical fibers.

it's coherent light that links different nodes around the world, linking computers.

What if we could use the notion of quantum entanglement?

So photons that could be sent along optical fibers can nevertheless be quantum entangled with other photons very far away from them.

You could use quantum information to communicate and link the world.

What if we had quantum computers that are linked via quantum information Now?

We would have something called the quantum Internet.

Quantum imaging is something that's developing.

There's this wonderful idea, what's called the entanglement camera, Whereby you have two particles of light, two photons.

One is visible in the visible range of the spectrum, and one is an infrared photon.

So what happens to one influences the behavior of the other.

Infrared light is very good at imaging, Particularly imaging biological tissue.

Whereas visible light is much better to create images in cameras.

So you send the infrared light to probe biological tissue, for example, looking for cancer, tumors.

And then the visible light will create an image of what the infrared light sees.

Even though the visible light has never been near the physical object itself, it's magically transferring this information Via quantum entanglement.

So these are devices that are already being built and already being used to help in medical imaging, for example.

The quantum computer, of course, Is the poster child of the second quantum revolution.

Quantum computers famously operate very differently from classical computers.

They don't rely on bits of information that are 0 or 1, but

rely on quantum bits of information, Qubits that are both 0 and 1 at the same time.

And this gives us scope for exponentially increasing the power of computations.

They're the ultimate in parallel processing.

A quantum computer, when we have it, Will one day be able to solve problems that the most powerful supercomputers we have today Would take billions of years to solve.

Quantum computers, we hope, Will be able to help us in new drug discoveries, in better climate models, in financial transactions, in studying the behavior of quantum systems, in research labs, in physics and chemistry.

they will have specialized applications that are Going to change the world.

There are, of course, many challenges still ahead of us.

For example, in a quantum computer, it's not just about having a qubit that can be off and on at the same time.

You have to have many qubits quantum entangled together.

And together they form the quantum processor that can run quantum algorithms that can carry out computations down in the quantum realm.

But of course, linking these qubits together Via entanglement Is subject to disturbance from outside, what's called decoherence.

The idea that the quantum effects are very delicate and ephemeral, and

they will dissipate very quickly, like putting a hot cup of coffee in the freezer, you know, it won't stay hot.

Well, in the quantum world, decoherence happens very, very fast.

And one of the biggest challenges is how do you maintain these, the quantumness of your computer for long enough for it to do the computations.

This is related to what's called quantum error correction.

You have to build in a certain redundancy.

So if you need 100 qubits to carry out a computation, you probably need a thousand or a million, just to make sure that collectively you get an answer, Even though some of them are useless because of decoherence.

Another problem is, of course, what do you build a quantum computer with?

What's called the substrate would be, what is the hardware that the quantum computer will be?

There are lots of candidates, and we don't know which is the best one.

Maybe they will be using what's called superconducting circuits, electrical circuits that are at temperatures near absolute zero, such that this quantum effect called superconductivity, and

suddenly appears where you have electrical currents flowing through wires with zero resistance.

Now you can start to use these superconducting wires to carry out quantum effect quantum computations.

You could build a quantum computer out of light, out of photons of light traveling through fibers.

You can build it out of clouds of atoms that are suspended in a magnetic field and held in place and cooled down to near absolute zero by laser beams.

And those atoms, then they can be pumped with energy with other lasers, such that you put them into a quantum superposition of being in two energy states at the same time.

So now you have clouds of atoms that form your quantum computer.

You can have strings of atoms that are missing or have extra electrons.

So they're ions, they're electrically charged.

The fact they have electric charge means you can hold them in place Using electric and magnetic fields.

We don't know which is going to be the best one.

And then even when you build a quantum computer, what do you run on it?

What's the code that you write that's going to carry out a quantum computation?

Subtitles ListPlay Video

Nature may have already solved the problem stumping quantum physicists | Jim Al-Khalili

process

figure

multiple

artificial