Ramsey interference in a multilevel quantum system

Abstract

We report Ramsey interference in the excitonic population of a negatively charged quantum dot measured in resonant fluorescence. Our experiments show that the decay time of the Ramsey interference is limited by the spectral width of the transition. Applying a vertical magnetic field induces Zeeman split transitions that can be addressed by changing the laser detuning to reveal two-, three-, and four-level system behavior. We show that under finite field the phase-sensitive control of two optical pulses from a single laser can be used to prepare both population and spin states simultaneously. We also demonstrate the coherent optical manipulation of a trapped spin in a quantum dot in a Faraday geometry magnetic field.

Cavity-enhanced coherent light scattering from a quantum dot

“…The fraction of the total emitted light due to RRS ( 7 , 22 ) is where T 1 is the radiative lifetime and T 2 = 2 ħ /Δ E . For an emitter with no cavity enhancement, we typically see T 1 = 1 ns and T 2 = 0.6 ns ( 21 ), which would lead to a variation in I RRS , as shown in Fig. 2C (in blue).…”

“…Optical pulses of 57 ps length resonantly excite the transition, and Rabi oscillations in the detected RE are observed as a function of the incident field amplitude. The source was driven with 0.71π pulses to provide a near-deterministic excitation and an optimal signal-to-background level ( 18 , 21 ). When two pulses are used to excite the source at a time separation of 2.36 ns, the emitted photons can again be interfered to determine their indistinguishability.…”

Coherent superpositions of three states for phosphorous donors in silicon prepared using THz radiation

“…Similar experiments have been carried out on optical transitions in semiconductors 13 , but it is known that in free space atoms one is able to gain better control by including many orbital eigenstates in the wavepacket 10 13 . The importance of control over neighbouring qubit interactions in silicon has been shown separately 6 7 9 13 , and it is also appreciated that control over interactions is important for the implementation of surface code error quantum correction 14 15 16 17 . A convenient radiation source for coherent studies in the THz spectral region is the free-electron laser.…”

“…Optical control of Rydberg orbits of trapped atoms in vacuum has provided high-fidelity gate interactions9 and fine control over the electron trajectory10, with applications in atomic clocks and quantum computing1112. Similar experiments have been carried out on optical transitions in semiconductors13, but it is known that in free space atoms one is able to gain better control by including many orbital eigenstates in the wavepacket1013. The importance of control over neighbouring qubit interactions in silicon has been shown separately67913, and it is also appreciated that control over interactions is important for the implementation of surface code error quantum correction14151617.…”

Self‐Assembled InAs/GaAs Coupled Quantum Dots for Photonic Quantum Technologies

“…The absence of a single optically excited state with strong transitions to both logical basis states prevents the use of lambda transitions that are the well‐established mechanism for optical generation of coherent superpositions of qubit basis states. We note that weak mixing of the spin states has previously been exploited to perform spin initialization and to create, via second‐order interactions, coherent superpositions of electron spin states under high pulse powers . The most common solution in single QDs has been the application of transverse magnetic fields, for example, along the x axis, which mixes the spin manifolds and enables lambda transitions .…”