Delayed-Choice quantum eraser experiment with an IBM quantum computer

The history of qubit q[0] was interpreted by means of two different entanglements using q[1], q[2], q[3], q[4]: on the z-basis, one entanglement was |E1> ∝ ( |0>₀ |1>₁ |0>₂ |0>₃ |0>₄ + exp(iφ) |1>₀ |0>₁ |0>₂ |0>₃ |0>₄. The other entanglement, on the z and x basis, was |E2> ∝ d(φ)|0>₀ |0>₁ |1>₂ |+>₃ |1>₄ + f(φ) |1>₀ |0>₁ |1>₂ |->₃ |1>₄ + g(φ) |0>₀ |0>₁ |1>₂ |->₃ |0>₄ + h(φ)|1>₀ |0>₁ |1>₂ |+>₃ |0>₄ ; |E2> allowed to interpret the probability of q[0] to be ∝ |d(φ)|² , |f(φ)|² , |g(φ)|² , or |h(φ)|² in relation to the measurements of other qubits; each of those probabilities had either the form ∝ cos² (φ/2) or ∝ sin²(φ/2); by associating those probabilities with q[0], the history of q[0] could be interpreted to be either A₀(φ)|0>₀ + B₀(φ)|0>₀ or C₀(φ)|1>₀ + D₀(φ)|1>₀, contrasting the pattern obtained when |E1> happened; no interference pattern was detected without the measurements of q[0] when |E2> happened. In this way, neither the gates on q[0] nor |E1> created an interference pattern; the interference pattern was the result of |E2> and could be attributed to q[0] when joint measurements with the other qubits were performed. Measurements on q[0] were performed first, which were interpreted as “erasing” the history that q[0] would have had before it was measured with the other qubits in |E2>. Results obtained with the present experiment, and its analysis, offered a new interpretation to Schully’s Delayed-Choice Quantum eraser experiment.