What is Qubit? Single Qubit and Multiple Qubit?
Qubit gates, also known as quantum gates, are operations that act on qubits in a quantum computer. They are analogous to logic gates in classical computing but operate on the quantum states of qubits instead of classical bits. Qubit gates are essential for manipulating and transforming the quantum states of qubits, allowing for the execution of quantum algorithms.
Single Qubit Gates: Single qubit gates act on individual qubits and are represented by unitary matrices. These gates can modify the quantum state of a single qubit without affecting other qubits in a quantum system. Some commonly used single qubit gates include:
- Pauli-X gate (bit flip gate): It flips the state of a qubit from 0 to 1 or from 1 to 0.
- Pauli-Y gate: It performs a rotation around the Y-axis of the Bloch sphere, modifying the relative phase of the qubit state.
- Pauli-Z gate (phase flip gate): It flips the phase of the qubit, changing the sign of the state |1⟩.
- Hadamard gate: It creates a superposition by transforming the |0⟩ state to an equal superposition of |0⟩ and |1⟩.
Multiple Qubit Gates: Multiple qubit gates act on two or more qubits simultaneously, allowing for entanglement and interactions between qubits. These gates are represented by higher-dimensional unitary matrices. Some commonly used multiple qubit gates include:
. CNOT gate (controlled-NOT gate): It performs a NOT operation on the target qubit (flips the state) if the control qubit is in the state |1⟩, creating entanglement between the two qubits.
- SWAP gate: It exchanges the states of two qubits, useful for rearranging quantum information.
- Controlled-phase gate: It introduces a phase shift on the target qubit depending on the state of the control qubit.
Multiple qubit gates play a crucial role in quantum algorithms, such as quantum teleportation, quantum error correction, and quantum algorithms for factorization and optimization.
By combining single and multiple qubit gates, quantum circuits can be constructed to perform complex computations and manipulate quantum states, enabling the execution of quantum algorithms with the potential for quantum speedup compared to classical computation.