University of Pennsylvania Demonstrates Single-Gate Parallel Entanglement on Room-Temperature Diamond Quantum Register

Quantum researchers at the University of Pennsylvania have demonstrated single-gate, parallelized multipartite entanglement on a solid-state quantum register operating under ambient room-temperature conditions. Detailed in a study published in Nature Nanotechnology, the team generated a four-qubit Greenberger–Horne–Zeilinger (GHZ) state—entangling the central electron spin of a nitrogen-vacancy (NV) center in diamond with three surrounding ¹³C nuclear spin memory qubits—in 14.8 microseconds using a single dynamical decoupling (DD) control sequence.

Traditional solid-state central spin registers rely on sequential, pairwise two-qubit gates to entangle the central electron with individual nuclear memory qubits. This sequential approach incurs significant gate latency and introduces unwanted phase crosstalk on non-targeted nuclear spins. The UPenn framework harnesses this inherent crosstalk, tuning the unit-pulse timing (t) and repeat count (N) of an XY8 dynamical decoupling sequence to execute conditional rotations across multiple weakly coupled nuclear qubits simultaneously. The resulting 14.8 μs gate duration represents a 10-fold speedup over sequential gate protocols and operates near the physical interaction limit dictated by the perpendicular hyperfine coupling frequencies (A_⊥ ≈ 60 kHz).