When Google (GOOGL) unveiled its latest quantum chip in December, it said Willow achieved an almost three-decade-long challenge in the world of quantum computing.
The tech giant said Willow was able to reduce the rate of errors during a computation despite adding more qubits, or units of computation in quantum computers. The chip demonstrated a breakthrough for the field, which promises computers that can solve computations beyond the ability of classical computers.
For example, Google said Willow was able to complete a computation in less than five minutes that would take a classical computer from the beginning of the universe until now to complete.
In recent years, researchers have made progress toward actually building quantum computers, and are currently experimenting with them for things like discovering new materials and drug research.
Here’s a glossary to get you acquainted with the world of quantum computing.
While classical computers (such as the one you’re likely using right now to read this glossary) use bits that represent 0s and 1s, quantum computers use quantum bits — or qubits— which are usually electrons, photons, or another subatomic particles.
Connected together, qubits have far more processing power than binary 0s and 1s.
IBM (IBM), Rigetti Computing, and other companies working on quantum computing use superconducting circuits that are colder than deep space to generate and control qubits, according to MIT Technology Review. IonQ (IONQ), another quantum computing company, uses ultra-high-vacuum chambers where individual atoms are trapped in an electromagnetic field on a silicon chip.
Quantum computers can generate and control qubits to perform computations. However, the more qubits that are used, the more errors typically occur in a computation.
“Errors are one of the greatest challenges in quantum computing,” according to Hartmut Neven, founder and lead of Google Quantum AI, because they “have a tendency to rapidly exchange information with their environment, making it difficult to protect the information needed to complete a computation.”
Google Willow’s ability to cut the error rate in half despite adding more qubits was a “historic accomplishment” known as “‘below threshold,’ or being able to drive errors down while scaling up the number of qubits,” Neven said.
So how can quantum computers be millions and millions of years faster than even the most powerful supercomputer? That lies in the ability of qubits to be 0 and 1 at the same time — a state called superposition.
In superposition, qubits don’t have a value until the quantum computer finishes calculating, and can represent any possible combination of 0 and 1 simultaneously. While qubits are in superposition, a quantum computer can calculate several potential solutions at the same time.
When a quantum computer finds a solution and the qubits are measured, they “collapse” to either a 0 or 1.
When a pair of qubits exist in a single quantum state, it’s referred to as entanglement.
In entanglement, if the state of one of the qubits is changed, the state of the other will instantly change in a predictable way — even if the qubits are far away from each other.
Decoherence is when qubits lose their quantum state from an interaction with their environment. Qubits can fall out of superposition due to “noise” such as a change in temperature or vibrations.
The delicacy of the quantum state makes the aforementioned super cold superconductor circuits and ultra-high-vacuum chambers necessary.
When qubits in a state of superposition interact, this is called interference. During interference, the qubits’ probabilities are either reinforced, known as constructive interference, or cancelled, which is called destructive interference.
Interference occurs due to the wave-like nature of electrons, photons, and other quantum particles.
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