Angular momentum transfer from photon polarization to an electron spin in a gate-defined quantum dot

Abstract

Gate-defined quantum dots (QDs) are such a highly-tunable quantum system in which single spins can be electrically coupled, manipulated, and measured. However, the spins in gate-defined QDs are lacking its interface to free-space photons. Here, we verify that a circularly-polarized single photon can excite a single electron spin via the transfer of angular momentum, measured using Pauli spin blockade (PSB) in a double QD. We monitor the inter-dot charge tunneling which only occur when the photo-electron spin in one QD is anti-parallel to the electron spin in the other. This allows us to detect single photo-electrons in the spin-up/down basis using PSB. The photon polarization dependence of the excited spin state was finally confirmed for the heavy-hole exciton excitation. The angular momentum transfer observed here is a fundamental step providing a route to instant injection of spins, distributing single spin information, and possibly towards extending quantum communication.

Chiral Light Emission from a Sphere Revealed by Nanoscale Relative-Phase Mapping

“… 3 , 4 CPL, classified by its parity as having right- or left-handed circular polarization (RCP, LCP), can be utilized as a digital signal carrier. 5 , 6 Compared to linearly polarized light, which can convey polarization information in an analog manner, CPL provides a more robust platform for information transfer that has been adopted even in biological systems. 7 , 8 However, light sources used in quantum circuits, such as single-photon generators, consist of linear optical dipoles typically hosted on molecules, atomic defects, or few-nanometer quantum dots, which are not capable of encoding CPL information unless one involves momentum transfer to electron spins under high magnetic field and low temperature.…”

Photogeneration of a single electron from a single Zeeman-resolved light-hole exciton with preserved angular momentum

“…We show that the photo-excitation of a pair of an electron and one of the spin-resolved LHs is prohibited by optical spin blockade for the case of the photo-generated electron spin being parallel to the residing electron spin in the N e = 1 SQD. Next, we compare the result with a spin readout method for the photo-electron with a double QD (DQD) [11]. We detect the spin orientation (up or down) of the photo-generated electron in the spin-resolved LH excitation using the electrical Pauli spin blockade effect.…”

“…The first QW wafer used here is specially designed such that electron Zeeman energy is larger than the excitation light band width (∆ν photon =0.6 meV) and the Zeeman splitting LH-or LH+ state is well resolved. The Zeeman energy is estimated to be 162 µeV (< ∆ν photon ) for electrons, assuming the g-factor of -0.4 [14], and 3 meV (> ∆ν photon ) for LHs, assuming the g-factor of -3.5 [15,16] under a large in-plane magnetic field, B // = 7 T. The magnetic field is chosen to be large enough to polarize the electron spin but not so large as to reduce the spin lifetime below the readout time [11]. We find that the SQD device used here has large enough HH-LH separation to be able to resolve the LH-state excitation for the photon-trapping experiment.…”

“…This is not the case for the H-polarized photon excitation, because a triplet state of T + (1, 1) with two up spins is created and the inter-dot electron tunneling is blocked by Pauli exclusion. Consequently, the difference of the photogenerated spin configuration, parallel or antiparallel, can be distinguished in a single-shot measurement of the charge change in the DQD (Supplementary information 4) [11]. Note that a photo-electron can be created in either dot of the DQD, and therefore we only used the post-selected events of photo-electron trapping in the left dot to derive the probability of finding the parallel or antiparallel spin configuration.…”

Circular Polarization Discrimination Enhanced by Anisotropic Media

“…Owing to the superior robustness of circular polarization states during transmission, [ 1 ] during asymmetrical interaction with chiral matters, [ 2 ] and in the quantum information carried by its photon spin states, [ 3 ] circularly polarized light has promising applications in optical communication, [ 4 ] imaging, [ 5 ] sensing, [ 6 ] and quantum information processing. [ 7–9 ] To promote the advancement of CPL‐related technologies, the development of compact optoelectronic devices, that can distinguish the chirality, or spin state of CPL, is a central task. Based on their asymmetrical interaction with LCP and RCP light, natural chiral materials have been made into photon spin discriminative detectors [ 10,11 ] and emitters.…”