To entangle two qubits, you can use various methods depending on the physical system you are working with. Here is a general procedure for entangling two qubits:
Preparation: Start with two qubits in a known initial state, often referred to as |0⟩ or |1⟩. For example, if you have two electron spins, you can prepare them both in the spin-up state |↑⟩.
Apply an entangling gate: Use a quantum gate operation to perform an entangling operation on the qubits. One common entangling gate is the Controlled-NOT (CNOT) gate. The CNOT gate flips the second qubit (the target qubit) if the first qubit (the control qubit) is in the state |1⟩. This gate creates an entangled state between the two qubits.
Resulting entangled state: After applying the entangling gate, the two qubits will be in an entangled state, which cannot be described independently for each qubit. The specific form of the entangled state depends on the initial state and the gate used.
It's important to note that the entangling operation can introduce entanglement between qubits while preserving the information contained in the individual qubits. The resulting entangled state can exhibit correlations that are stronger than classical correlations, and measuring one qubit can instantaneously affect the state of the other, even if they are physically separated.
The process of entangling qubits is a fundamental building block for various quantum computing and quantum communication protocols. Different physical systems, such as trapped ions, superconducting circuits, or photons, have their specific methods for creating and manipulating entangled qubits, but the general idea remains consistent across platforms.