Two-qubit gates using on-demand single-photons from ordered shape and size controlled large-volume superradiant quantum dots

At scale, fault tolerant on-chip photonic quantum information processing (P-QIP) has been hindered by the lack of (1) on-demand generation of millions of indistinguishable single photons as qubits from (2) quantum emitters in designed spatially ordered arrays. The demonstrated unique shape- and size-controlled mesa-top single quantum dots (MTSQDs) positioned with nm accuracy in designed arrays and exhibiting <2 nanometer spectral nonuniformity offer a promising solution. Here we report CNOT gates with ~90% fidelity using photons from individual MTSQDs at 4 K without Purcell enhancement that enable generating Bell states with fidelity of 0.825 ± 0.010, both underpinned by a two-photon interference (TPI) visibility 0.945 ± 0.005 and single photon purity > 99.5%. Temperature and power dependent studies reveal these remarkable figures-of-merit to originate in single photon superradiance and weak electron-phonon coupling unique to large volume MTSQDs giving large oscillator strength ( ~ 30) thus robustness against temperature. These results show a path to utility scale P-QIP platforms utilizing MTSQD arrays.