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.
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