Quantum computers could eventually outstrip the computational limits of classical computers. They rely on the behavior of atomic and subatomic particles, whose quantum states are incredibly fragile and easily destroyed— which is why this technology remains largely theoretical. How would quantum computers work, and are they really possible? Chiara Decaroli investigates.
Lesson by Chiara Decaroli, directed by Artrake Studio.
Lesson by Chiara Decaroli, directed by Artrake Studio.
Category
📚
LearningTranscript
00:00The contents of this metal cylinder could either revolutionize technology or be completely useless.
00:13It all depends on whether we can harness the strange physics of matter at very, very small scales.
00:19To even have a chance of doing so, we have to control the environment precisely.
00:23The thick tabletop and legs guard against vibrations from footsteps, nearby elevators, and opening or closing doors.
00:30The cylinder is a vacuum chamber, devoid of all the gases in the air.
00:34Inside the vacuum chamber is a smaller, extremely cold compartment, reachable by tiny laser beams.
00:40Inside are ultra-sensitive particles that make up a quantum computer.
00:45So what makes these particles worth the effort?
00:48In theory, quantum computers could outstrip the computational limits of classical computers.
00:54Classical computers process data in the form of bits.
00:58Each bit can switch between two states labeled 0 and 1.
01:03A quantum computer uses something called a qubit, which can switch between 0, 1, and what's called a superposition.
01:11While the qubit is in its superposition, it has a lot more information than 1 or 0.
01:17You can think of these positions as points on a sphere.
01:20The north and south poles of the sphere represent 1 and 0.
01:24A bit can only switch between these two poles.
01:27But when a qubit is in its superposition, it can be at any point on the sphere.
01:32We can't locate it exactly.
01:34The moment we read it, the qubit resolves into a 0 or a 1.
01:38But even though we can't observe the qubit in its superposition,
01:42we can manipulate it to perform particular operations while in this state.
01:46So as a problem grows more complicated, a classical computer needs correspondingly more bits to solve it.
01:53While a quantum computer will theoretically be able to handle more and more complicated problems
01:59without requiring as many more qubits as a classical computer would need bits.
02:04The unique properties of quantum computers result from the behavior of atomic and subatomic particles.
02:10These particles have quantum states, which correspond to the state of the qubit.
02:15Quantum states are incredibly fragile, easily destroyed by temperature and pressure fluctuations,
02:21stray electromagnetic fields, and collisions with nearby particles.
02:25That's why quantum computers need such an elaborate setup.
02:29It's also why, for now, the power of quantum computers remains largely theoretical.
02:36So far, we can only control a few qubits in the same place at the same time.
02:41There are two key components involved in managing these fickle quantum states effectively.
02:46The types of particles a quantum computer uses, and how it manipulates those particles.
02:52For now, there are two leading approaches, trapped ions and superconducting qubits.
02:58A trapped ion quantum computer uses ions as its particles and manipulates them with lasers.
03:05The ions are housed in a trap made of electrical fields.
03:09Inputs from the lasers tell the ions what operation to make by causing the qubit state to rotate on the sphere.
03:16To use a simplified example, the lasers could input the question,
03:20what are the prime factors of 15?
03:23In response, the ions may release photons.
03:26The state of the qubit determines whether the ion emits photons, and how many photons it emits.
03:32An imaging system collects these photons and processes them to reveal the answer, 3 and 5.
03:39Superconducting qubit quantum computers do the same thing in a different way,
03:43using a chip with electrical circuits instead of an ion trap.
03:47The states of each electrical circuit translate to the state of the qubit.
03:51They can be manipulated with electrical inputs in the form of microwaves.
03:56So, the qubits come from either ions or electrical circuits, acted on by either lasers or microwaves.
04:03Each approach has advantages and disadvantages.
04:06Ions can be manipulated very precisely, and they last a long time.
04:11But as more ions are added to a trap, it becomes increasingly difficult to control each with precision.
04:17We can't currently contain enough ions in a trap to make advanced computations.
04:22But one possible solution might be to connect many smaller traps that communicate with each other via photons,
04:29rather than trying to create one big trap.
04:32Superconducting circuits, meanwhile, make operations much faster than trapped ions,
04:37and it's easier to scale up the number of circuits in a computer than the number of ions.
04:43But the circuits are also more fragile and have a shorter overall lifespan.
04:48And as quantum computers advance, they will still be subject to the environmental constraints needed to preserve quantum states.
04:55But in spite of all of these obstacles, we've already succeeded at making computations in a realm we can't enter or even observe.
05:03Dive deeper into the world of quantum mechanics with this playlist.
05:07Dive deeper into the world of quantum mechanics with this playlist.
05:09Dive deeper into the world of quantum mechanics with this playlist.