114 research outputs found
Quantum properties of multipole radiation
Cataloged from PDF version of article.In this study, multipole expansion of quantum electromagnetic radiation is
constructed and quantized by canonical transformation with increasing demand
of some modern research areas of physics such as entanglement of the orbital
angular momentum states, novel experiments with trapped atoms, and the atomic
and molecular transitions with given angular momentum.
Also, the SU(2) invariance of quantum field and the rotational symmetry of
vacuum noise of polarization with respect to source location are proved.
It is shown that, at any point we can construct a proper frame in which
the description of polarization is reduced to a conventional (2 × 2) polarization
matrix. And peculiarities of electric and magnetic-type zero-point oscillations
were examined, and as a result it is shown that the monochromatic zeropoint
oscillations of all types and modes, have constant level in the volume of
quantization.
Finally, the complete local representation of photon operators, which
correspond to the states of photons with given projection of angular momentum
at any point, is constructed for the possible utility of near-field optics.Soykal, Öney OrhunçM.S
Size-dependence of Strong-Coupling Between Nanomagnets and Photonic Cavities
The coherent dynamics of a coupled photonic cavity and a nanomagnet is
explored as a function of nanomagnet size. For sufficiently strong coupling
eigenstates involving highly entangled photon and spin states are found, which
can be combined to create coherent states. As the size of the nanomagnet
increases its coupling to the photonic mode also monotonically increases, as
well as the number of photon and spin states involved in the system's
eigenstates. For small nanomagnets the crystalline anisotropy of the magnet
strongly localized the eigenstates in photon and spin number, quenching the
potential for coherent states. For a sufficiently large nanomagnet the
macrospin approximation breaks down and different domains of the nanomagnet may
couple separately to the photonic mode. Thus the optimal nanomagnet size is
just below the threshold for failure of the macrospin approximation.Comment: 10 pages, 7 figure
Phonitons as a sound-based analogue of cavity quantum electrodynamics
A quantum mechanical superposition of a long-lived, localized phonon and a
matter excitation is described. We identify a realization in strained silicon:
a low-lying donor transition (P or Li) driven solely by acoustic phonons at
wavelengths where high-Q phonon cavities can be built. This phonon-matter
resonance is shown to enter the strongly coupled regime where the "vacuum" Rabi
frequency exceeds the spontaneous phonon emission into non-cavity modes, phonon
leakage from the cavity, and phonon anharmonicity and scattering. We introduce
a micropillar distributed Bragg reflector Si/Ge cavity, where Q=10^5-10^6 and
mode volumes V<=25*lambda^3 are reachable. These results indicate that single
or many-body devices based on these systems are experimentally realizable.Comment: Published PRL version. Note that the previous arXiv version has more
commentary, figures, etc. Also see http://research.tahan.com
Quantum properties of dichroic silicon vacancies in silicon carbide
The controlled generation and manipulation of atom-like defects in solids has
a wide range of applications in quantum technology. Although various defect
centres have displayed promise as either quantum sensors, single photon
emitters or light-matter interfaces, the search for an ideal defect with
multi-functional ability remains open. In this spirit, we investigate here the
optical and spin properties of the V1 defect centre, one of the silicon vacancy
defects in the 4H polytype of silicon carbide (SiC). The V1 centre in 4H-SiC
features two well-distinguishable sharp optical transitions and a unique S=3/2
electronic spin, which holds promise to implement a robust spin-photon
interface. Here, we investigate the V1 defect at low temperatures using optical
excitation and magnetic resonance techniques. The measurements, which are
performed on ensemble, as well as on single centres, prove that this centre
combines coherent optical emission, with up to 40% of the radiation emitted
into the zero-phonon line (ZPL), a strong optical spin signal and long spin
coherence time. These results single out the V1 defect in SiC as a promising
system for spin-based quantum technologies
High-fidelity spin and optical control of single silicon-vacancy centres in silicon carbide
Scalable quantum networking requires quantum systems with quantum processing capabilities. Solid state spin systems with reliable spin–optical interfaces are a leading hardware in this regard. However, available systems suffer from large electron–phonon interaction or fast spin dephasing. Here, we demonstrate that the negatively charged silicon-vacancy centre in silicon carbide is immune to both drawbacks. Thanks to its 4A2 symmetry in ground and excited states, optical resonances are stable with near-Fourier-transform-limited linewidths, allowing exploitation of the spin selectivity of the optical transitions. In combination with millisecond-long spin coherence times originating from the high-purity crystal, we demonstrate high-fidelity optical initialization and coherent spin control, which we exploit to show coherent coupling to single nuclear spins with ∼1 kHz resolution. The summary of our findings makes this defect a prime candidate for realising memory-assisted quantum network applications using semiconductor-based spin-to-photon interfaces and coherently coupled nuclear spins
Spectrally reconfigurable quantum emitters enabled by optimized fast modulation
The ability to shape photon emission facilitates strong photon-mediated
interactions between disparate physical systems, thereby enabling applications
in quantum information processing, simulation and communication. Spectral
control in solid state platforms such as color centers, rare earth ions, and
quantum dots is particularly attractive for realizing such applications
on-chip. Here we propose the use of frequency-modulated optical transitions for
spectral engineering of single photon emission. Using a scattering-matrix
formalism, we find that a two-level system, when modulated faster than its
optical lifetime, can be treated as a single-photon source with a widely
reconfigurable photon spectrum that is amenable to standard numerical
optimization techniques. To enable the experimental demonstration of this
spectral control scheme, we investigate the Stark tuning properties of the
silicon vacancy in silicon carbide, a color center with promise for optical
quantum information processing technologies. We find that the silicon vacancy
possesses excellent spectral stability and tuning characteristics, allowing us
to probe its fast modulation regime, observe the theoretically-predicted
two-photon correlations, and demonstrate spectral engineering. Our results
suggest that frequency modulation is a powerful technique for the generation of
new light states with unprecedented control over the spectral and temporal
properties of single photons.Comment: 9 pages, 6 figures; Supplementary Informatio
- …