A quantum bit, or qubit, is the fundamental building block of quantum computers. Like classical binary bits, qubits can store information, but they behave differently due to quantum mechanics. Qubits are typically made up of subatomic particles like photons or electrons, and their properties represent 1s and 0s in binary computing.
One key difference between qubits and classical bits is that qubits can occupy both states simultaneously – a phenomenon known as superposition. This means a qubit can exist in multiple states until it’s directly observed or disrupted by external factors like heat. To maintain this fragile quantum state, qubits must be kept free from interference and require very cold temperatures.
Superposition allows for exponential growth in the number of possible states available, making quantum computers potentially more powerful than classical ones. For example, two qubits can encode data in all four states at once, whereas two classical bits can only take on one of 16 possible combinations.
Entanglement, another key aspect of qubits, links the states of subatomic particles regardless of their distance. This means that gaining information about a qubit will automatically provide information about its entangled particle.
Quantum computers can theoretically perform complex calculations by combining superposition and entanglement. However, scaling up this technology is challenging due to the fragility of qubits. Qubits are prone to decoherence, where their quantum state collapses with even faint external influences like heat or movement. This requires specialized equipment and chilling them to near absolute zero.
To overcome these limitations, researchers are investigating error correction techniques, such as building logical qubits – groups of entangled, error-prone qubits that store the same information in different places. With sufficient stabilization, quantum computers can one day perform calculations in a fraction of the time it takes for binary computers and solve complex equations that are currently impossible to solve with today’s most powerful supercomputers.
Source: https://www.livescience.com/technology/computing/what-is-a-quantum-bit-qubit