Quantum electronics and coherent light

Hideo Kosaka, Hideki Shigyou, Yasuyoshi Mitsumori +5 more

We demonstrate that the superposition of light polarization states is coherently transferred to electron spins in a semiconductor quantum well. By using time‐resolved Kerr rotation we observe the initial phase of Larmor precession of electron spins whose coherence is transferred from light. To break the electron‐hole spin entanglement, we utilized the big discrepancy between the transverse g‐factors of electrons and light holes. The result encourages us to make a quantum media converter between flying photon qubits and stationary electron spin qubits in semiconductors.

S. Chua

Hideo Kosaka, Hideki Shigyou, Yasuyoshi Mitsumori +5 more

We demonstrate that the superposition of light polarization states is coherently transferred to electron spins in a semiconductor quantum well. By using time-resolved Kerr rotation, we observe the initial phase of Larmor precession of electron spins whose coherence is transferred from light. To break the electron-hole spin entanglement, we utilized the big discrepancy between the transverse g factors of electrons and light-holes. The result encourages us to make a quantum media converter between flying photon qubits and stationary electron-spin qubits in semiconductors.

Hideo Kosaka, Hideki Shigyou, Takeshi J. Inagaki +10 more

Spin is a quantum property of electrons. For spin‐based quantum information technology, preparation and read‐out of the electron spin state should be spin coherent. We demonstrate that the polarization coherence of light can be transferred to the spin coherence of electrons in a semiconductor quantum nanostructure, and the prepared coherence of the electron spin can also be read out with light by the developed tomographic Kerr rotation method. We also demonstrate that a single photon is efficiently converted (∼27%) into a single electron trapped in a gate‐defined quantum dot, where the g‐factor of electrons is tuned to zero, and the charge state is detected with an adjacent quantum point contact without destructing the spin state. We further demonstrate that the spin coherence of a single electron trapped in one of double quantum dots is electrically manipulated with a microwave applied to the gate and read out via the Pauli spin blockade phenomenon. All of these functions are needed to build all semiconductor quantum repeaters and distributed quantum computers.