Question

What devices or practical procedures are required for performing some computation with two entangled photon qubits in superposition of 0 and 1 until measurement, that illustrates how quantum computers are faster than classical computers?

Answer 1

Performing a computation that demonstrates the speedup of a quantum computer over classical computers typically involves implementing a quantum algorithm that showcases the advantages of quantum parallelism and interference. One such algorithm is the Bernstein-Vazirani algorithm. While I cannot provide a step-by-step procedure for performing the experiment, I can outline the basic elements involved:

1. Qubit Preparation: The experiment would start by preparing two entangled photon qubits in a superposition of 0 and 1. This typically involves a controlled process where two photons are generated and entangled using techniques such as spontaneous parametric down-conversion.

2. Quantum Gates: Quantum gates are applied to manipulate the state of the qubits and perform computations. In the Bernstein-Vazirani algorithm, a combination of Hadamard gates and controlled-NOT (CNOT) gates is typically used.

3. Oracle Function: The algorithm requires the definition of an oracle function, which is a black box function that encodes a secret bit string. The oracle function takes the input from the qubits and maps it to an output. The goal is to determine the hidden bit string.

4. Quantum Computation: By applying a series of Hadamard and CNOT gates, the algorithm interacts with the oracle function, using the entanglement and superposition properties of the qubits to extract information about the hidden bit string efficiently.

5. Measurement and Result: Finally, the qubits are measured, collapsing their states into classical bits. The measurements provide the outcome of the computation, revealing the hidden bit string.

The advantage of the Bernstein-Vazirani algorithm is that it solves a specific problem exponentially faster on a quantum computer compared to a classical computer. Classically, determining the hidden bit string would require evaluating the oracle function multiple times, while the quantum algorithm can find the solution in a single query.

While the experiment involving entangled photon qubits in the Bernstein-Vazirani algorithm may be challenging to perform practically, it serves as an example of how quantum computers can provide computational speedups over classical computers for certain problems. The parallelism and interference effects exhibited by quantum systems enable more efficient computations in specific scenarios.