2025/07/08 by Prajapati, Tomis, Mehta, Harsh, Banerjee, Shreya +2
#FOS: Physical sciences #Quantum Physics (quant-ph)
paper · doi:10.48550/arxiv.2507.07123
The experimental verification of multipartite entangled states is essential for advancing quantum information processing. Entanglement witnesses (EWs) provide a widely used and experimentally accessible approach for detecting genuinely multipartite entangled states. In this work, we theoretically derive the entanglement witness for the four-qubit Dicke state and experimentally evaluate it on two distinct IBM 127-qubit Quantum Processing Units (QPUs), namely ibm_sherbrook and ibm_brisbane. A negative expectation value of the witness operator serves as a sufficient condition for confirming genuine multipartite entanglement. We report the maximum (negative) values of the witness achieved on these QPUs as -0.178 ± 0.009 and -0.169 ± 0.002, corresponding to two different state preparation protocols. Additionally, we theoretically investigate the effect of various noise channels on the genuine entanglement of a four-qubit Dicke state using the Qiskit Aer simulator. We show the behavior of the EW constructed under the assumption of Markovian and non-Markovian amplitude damping and depolarizing noises, bit-phase flip noise, and readout errors. We also investigate the effect of varying thermal relaxation time on the EW, depicting a bound on the T1 time required for successful generation of a Dicke State on a superconducting QPU.