11 research outputs found
Spin-photon interface and spin-controlled photon switching in a nanobeam waveguide
Access to the electron spin is at the heart of many protocols for integrated
and distributed quantum-information processing [1-4]. For instance, interfacing
the spin-state of an electron and a photon can be utilized to perform quantum
gates between photons [2,5] or to entangle remote spin states [6-9].
Ultimately, a quantum network of entangled spins constitutes a new paradigm in
quantum optics [1]. Towards this goal, an integrated spin-photon interface
would be a major leap forward. Here we demonstrate an efficient and optically
programmable interface between the spin of an electron in a quantum dot and
photons in a nanophotonic waveguide. The spin can be deterministically prepared
with a fidelity of 96\%. Subsequently the system is used to implement a
"single-spin photonic switch", where the spin state of the electron directs the
flow of photons through the waveguide. The spin-photon interface may enable
on-chip photon-photon gates [2], single-photon transistors [10], and efficient
photonic cluster state generation [11]
High Purcell factor generation of indistinguishable on-chip single photons
On-chip single-photon sources are key components for integrated photonic quantum technologies. Semiconductor quantum dots can exhibit near-ideal single-photon emission, but this can be significantly degraded in on-chip geometries owing to nearby etched surfaces. A long-proposed solution to improve the indistinguishablility is to use the Purcell effect to reduce the radiative lifetime. However, until now only modest Purcell enhancements have been observed. Here we use pulsed resonant excitation to eliminate slow relaxation paths, revealing a highly Purcell-shortened radiative lifetime (22.7 ps) in a waveguide-coupled quantum dot–photonic crystal cavity system. This leads to near-lifetime-limited single-photon emission that retains high indistinguishablility (93.9%) on a timescale in which 20 photons may be emitted. Nearly background-free pulsed resonance fluorescence is achieved under π-pulse excitation, enabling demonstration of an on-chip, on-demand single-photon source with very high potential repetition rates
The Male-Produced Aggregation-Sex Pheromone of the Cerambycid Beetle Plagionotus detritus ssp. detritus
The number of longhorn beetles with confirmed aggregation-sex pheromones has increased rapidly in recent years. However, the species that have been studied most intensively are pests, whereas much less is known about the pheromones of longhorn beetles that are rare or threatened. We studied the cerambycid beetle Plagionotus detritus ssp. detritus with the goal of confirming the presence and composition of an aggregation-sex pheromone. This species has suffered widespread population decline due to habitat loss in Western Europe, and it is now considered threatened and near extinction in several countries. Beetles from a captive breeding program in Sweden were used for headspace sampling. Gas chromatography-mass spectrometry revealed that collections from males contained large quantities of two compounds, identified as (R)-3-hydroxy-2-hexanone (major component) and (S)-2-hydroxy-3-octanone (minor component), in addition to smaller quantities of 2,3-hexanedione and 2,3-octanedione. None of the compounds was present in collections from females. When tested singly in a field bioassay, racemic 3-hydroxy-2-hexanone and 2-hydroxy-3-octanone were not attractive to P. detritus, whereas a 5:1 blend elicited significant attraction. Both compounds are known as components of the pheromones of conspecific beetles, but, to our knowledge, this is the first cerambycid shown to use two compounds with different chain lengths, in which the positions of the hydroxyl and carbonyl functions are interchanged between the two. The pheromone has potential as an efficient tool to detect and monitor populations of P. detritus, and may also be useful in more complex studies on the ecology and conservation requirements of this species
Radiative Auger process in the single-photon limit
In a multi-electron atom, an excited electron can decay by emitting a photon.
Typically, the leftover electrons are in their ground state. In a radiative
Auger process, the leftover electrons are in an excited state and a redshifted
photon is created. In a semiconductor quantum dot, radiative Auger is predicted
for charged excitons. Here we report the observation of radiative Auger on
trions in single quantum dots. For a trion, a photon is created on
electron-hole recombination, leaving behind a single electron. The radiative
Auger process promotes this additional (Auger) electron to a higher shell of
the quantum dot. We show that the radiative Auger effect is a powerful probe of
this single electron: the energy separations between the resonance fluorescence
and the radiative Auger emission directly measure the single-particle
splittings of the electronic states in the quantum dot with high precision. In
semiconductors, these single-particle splittings are otherwise hard to access
by optical means as particles are excited typically in pairs, as excitons.
After the radiative Auger emission, the Auger carrier relaxes back to the
lowest shell. Going beyond the original theoretical proposals, we show how
applying quantum optics techniques to the radiative Auger photons gives access
to the single-electron dynamics, notably relaxation and tunneling. This is also
hard to access by optical means: even for quasi-resonant -shell excitation,
electron relaxation takes place in the presence of a hole, complicating the
relaxation dynamics. The radiative Auger effect can be exploited in other
semiconductor nanostructures and quantum emitters in the solid state to
determine the energy levels and the dynamics of a single carrier