Define bit and qubit. Explain the properties of a qubit.

Bit and Qubit – Definitions

Bit (Binary Digit)

• A bit is the basic unit of classical information.
• It can take on only one of two distinct states at a time:
  0 or 1.
• All classical computations are based on bits.

Qubit (Quantum Bit)

• A qubit is the quantum counterpart of a classical bit.
• It is the basic unit of information in quantum computing.
• Unlike a classical bit, a qubit can exist not just in the states |0⟩ or |1⟩, but also in a superposition of both.

Properties of Qubits

1. Aqubit can be in a superposed state of the two states
   0 and 1.
2. If measurements are carried out with a qubit in super
   posed state then the results that we get will be prob
   abilistic unlike how it’s deterministic in a classical
   computer.
3. Owing to the quantum nature, the qubit changes its
   state at once when subjected to measurement. This
   means, one cannot copy information from qubits the
   way we do in the present computers and is known as
   “no cloning principle”.
   AQubitcanbephysicallyimplementedbythetwostates
   of an electron or horizontal and vertical polarizations of
   photons as |↓⟩ and |↑⟩