Quantum bits, also known as qubits, are the basic unit of data in quantum computing. Like binary bits in classical computers, they can store information, but they behave very differently because quantum mechanics.
Quantum computer usually use subatomic particles, such as photons (packets of light) or electrons, as qubits. In qubits, properties such as charge, photonic polarization or spin represent 1s and 0s in binary computation. However, qubits are also subject to a phenomenon known as superposition And windingbecause of its quantum nature, this is where things start to get weird.
Bit vs qubit: What’s the difference?
In addition to being either 0 or 1, like bits, qubits can occupy both states at the same time — a superposition of 1 and 0. Qubits will remain in the superposition until they are directly observed or disturbed by external environmental factors, such as heat. Because these quantum states are so sensitive, qubits must be kept free from disturbance, which requires extremely cold temperatures.
Superposition allows a quantum computer’s qubits to be in multiple states (0, 1 or both) and the number of possible states increases exponentially the more qubits there are. If you have two classical bits, for example, at any given time, they can both take the values 0.0; 0.1; 1.0; or 1.1.
With two qubits, you can encode data in all four states at once. This means that quantum computers have the potential to have far more processing power than conventional computers that use binary bits. The more qubits you have, the more calculations you can process in parallel — and this increases exponentially as you add more to the system. But to see exponential growth in processing power, you have to involve qubits, too.
How does attachment work?
In quantum entanglement, the states of subatomic particles are linked, regardless of how far apart they are. Gaining information about a qubit automatically provides information about the entangled particles.
Entangled particles are always in a correlated state. Consequently, if a property (such as the spin) of one particle is measured, thereby taking it out of superposition, the same thing will happen immediately to the entangled particle. Since the states of two entangled particles are always correlated, knowing the state of one entangled particle means that the state of the other particle can be inferred.
Related: Quantum processor prototype boasts record 99.9% qubit fidelity
Rather than measuring the qubit directly, and thereby causing it to lose its superposition state, scientists investigated whether there might be a way to indirectly infer information about the qubit from its interactions with its surroundings.
Quantum entanglement of qubits also allows them to interact with each other simultaneously, regardless of their distance from each other. When combined with superposition, quantum entanglement theoretically allows qubits to significantly increase the computing power of quantum computers, allowing them to perform complex calculations that state-of-the-art binary computers would struggle to solve.
This is currently possible on a small scale, but the challenge is to scale it up. For example, some calculations, such as cracking an encryption algorithm, would take a classical computer millions of years to perform. However, if we could build a quantum computer with millions of qubits, those same algorithms could be solved in seconds.
Why are qubits so fragile and susceptible to decoherence?
So why don’t we stack more qubits to build such a machine? Unfortunately, qubits are short-lived, and their superpositions can collapse under very weak external environmental influences, such as heat or motion. For that reason, qubits are considered “noisy” and error-prone.
Therefore, many qubits need to be cooled to near zero. absolute zero and maintained using special equipment. They also have a very short “coherence time” — which is a measure of how long they maintain the desired state needed to process quantum calculations. The coherence time typically lasts only fraction of a second(The world record is 10 minutes for one qubit — but experts say this is unlikely to translate to real quantum computers.) This factor also makes qubits unsuitable for long-term data storage.
Although many quantum computers exist today, we still need to apply “error correction” techniques to the qubits to trust their results. One of the main error correction methods currently being investigated is building “logical qubit“A logical qubit is actually a group of interconnected, error-prone qubits that store the same information in different places. This spreads out possible points of failure during a computation, allowing errors to be corrected. If the qubits are sufficiently stabilized, with superposition and quantum entanglement of qubits, quantum computers could one day perform calculations in much faster time than binary computers, and solve complex equations that are impossible for modern computers to do.” the most advanced supercomputer.
