Demonstration of Scully-Drühl-type quantum erasers on quantum
  computers
We present a novel quantum circuit that genuinely implements the
Scully-Dr\"uhl-type delayed-choice quantum eraser, where the two recorders of
the which-way information directly interact with the signal qubit and remain
spatially separated. Experiments conducted on IBM Quantum and IonQ processors
demonstrate that the recovery of interference patterns, to varying degrees,
aligns closely with theoretical predictions, despite the presence of systematic
errors. This quantum circuit-based approach, more manageable and versatile than
traditional optical experiments, facilitates arbitrary adjustment of the
erasure and enables a true random choice in a genuine delayed-choice manner. On
the IBM Quantum platform, delay gates can be employed to further defer the
random choice, thereby amplifying the retrocausal effect. Since gate operations
are executed sequentially in time, the system does not have any involvement of
random choice until after the signal qubit has been measured, therefore
eliminating any potential philosophical loopholes regarding retrocausality that
might exist in other experimental setups. Remarkably, quantum erasure is
achieved with delay times up to $\sim1\,\mu\text{s}$ without noticeable
decoherence, a feat challenging to replicate in optical setups.
Bo-Hung Chen Dah-Wei Chiou Hsiu-Chuan Hsu