661 research outputs found
Giant -factors of Natural Impurities in Synthetic Quartz
We report the observation of -factors of natural paramagnetic impurities
in a pure synthetic quartz crystal at milli-Kelvin temperatures. Measurements
are made by performing spectroscopy using multiple high- Whispering Gallery
Modes sustained in the crystal. Extreme sensitivity of the method at low
temperatures allows the determination of natural residual impurities introduced
during the crystal growth. We observe -factors that significantly differ
from integer multiples of the electron -factor in vacuum, and with values of
up to , which reveals much stronger coupling between impurities and the
crystal lattice than in previous studies. Both substitutional and interstitial
ions are proposed as candidates for the observed interactions
Jump Chaotic Behaviour of Ultra Low Loss Bulk Acoustic Wave Cavities
We demonstrate a previously unobserved nonlinear phenomenon in an ultra-low
loss quartz Bulk Acoustic Wave cavity (), which only occurs
below 20 milli-Kelvin in temperature and under relatively weak pumping. The
phenomenon reveals the emergence of several stable equilibria (at least two
foci and two nodes) and jumps between these quasi states at random times. The
degree of this randomness as well as separations between levels can be
controlled by the frequency of the incident carrier signal. It is demonstrated
that the nature of the effect lays beyond the standard Duffing model
Collective Behaviour of Cr ions in Ruby Revealed by Whispering Gallery Modes
We present evidence for collective action of Cr ion impurities in a
highly doped ruby crystal at microwave frequencies. The cylindrical geometry of
the crystal allows for the creation of a superradiant, or "spin-mode" doublet,
with spatial structure similar to that of microwave whispering gallery modes
(WGMs). This results in a strict criteria of selection rules regarding the
interaction of resonant WGMs and spin-modes; namely that only modes with the
same wavenumber and azimuthal phase may interact. What results is an avoided
level crossing between the two, in which both WGM doublet constituents are seen
to interact with the spin resonance. We demonstrate that a four harmonic
oscillator model is necessary to accurately describe this result.Comment: 5 pages, 5 figure
Spin-Photon Interaction in a Cavity with Time-Reversal Symmetry Breaking
Employing a sapphire whispering gallery mode resonator, we demonstrate
features of the spin-photon interaction in cavities with broken time-reflection
symmetry. The broken symmetry leads to a lifting of the degeneracy between
left-handed and right-handed polarised cavity photons, which results in an
observable gyrotropic effect. In the high- cavity limit, such a situation
requires a modification of the Tavis-Cummings Hamiltonian to take into account
conservation of spin angular momentum and the corresponding selection rules. As
a result, the system is represented by a system of two linearly coupled bosonic
modes, with each one coupled to its own sub-ensemble of two-level systems with
different energy splittings. In the experimental example, these sub-ensembles
originate from Fe impurity ions effectively seen as a two level systems
at the interaction frequency. The temperature dependence of the population of
each sub-ensemble (in terms of effective susceptibility of the medium) is
determined experimentally in accordance with the theoretical predictions
revealing various paramagnetic impurity types in the solid. The regimes of
backscatterer and spin ensemble domination are discussed and compared.Comment: Phys. Rev. B, 201
Controlling a whispering gallery doublet mode avoided frequency crossing: Strong coupling between photon bosonic and spin degrees of freedom
A combination of electron spin interactions in a magnetic field allows us to
control the resonance frequencies of a high-Q Whispering Gallery (WG) cavity
mode doublet, resulting in precise measurements of an avoided crossing between
the two modes comprising the doublet. We show that the resonant photons
effectively behave as spin-- particles and that the physical
origins of the doublet phenomenon arise from an energy splitting between the
states of photon spin angular momentum. The exclusive role of the photon spin
in splitting the mode frequency is emphasized, and we demonstrate that the
gyrotropic and anisotropic properties of the crystalline media supporting the
WG mode lead to strong coupling between the bosonic and spin degrees of freedom
of cavity photons. Despite the demonstrated similarities with Jaynes-Cummings
type systems, the mode doublet system exhibits a significant difference due to
its linearity. Unlike traditional experiments dealing with interactions between
fields and matter, here the crystalline medium plays a role of macroscopic
symmetry breaking, assisting in the strong coupling between these photon
degrees of freedom. Such a regime is demonstrated experimentally with a method
to effectively control the photon spin state. Our experiments demonstrate for
the first time, controllable time-reversal symmetry breaking in a high-
cavity.Comment: Phys. Rev. A, 201
Strong Coupling between Whispering Gallery Modes and Chromium Ions in Ruby
We report the study of interactions between cavity photons and paramagnetic
Cr spins in a ruby (Cr:AlO) Whispering Gallery mode (WGM)
resonator. Examining the system at microwave frequencies and millikelvin
temperatures, spin-photon couplings up to 610 MHz or about 5% of photon energy
are observed between the impurity spins and high quality factor ()
WGM. Large tunability and spin-spin interaction allows operation in the strong
coupling regime. The system exhibits behaviour not predicted by the usual
Tavis-Cummings model because of interactions within the two-level spin bath,
and the existence of numerous photonic modes
Ultrasensitive microwave spectroscopy of paramagnetic impurities of sapphire crystals at millikelvin temperatures
Progress in the emerging field of engineered quantum systems requires the
development of devices that can act as quantum memories. The realisation of
such devices by doping solid state cavities with paramagnetic ions imposes a
trade-off between ion concentration and cavity coherence time. Here, we
investigate an alternative approach involving interactions between photons and
naturally occurring impurity ions in ultra-pure crystalline microwave cavities
exhibiting exceptionally high quality factors. We implement a hybrid Whispering
Gallery/Electron Spin Resonance method to perform rigorous spectroscopy of an
undoped single-crystal sapphire resonator over the frequency range 8--19 GHz,
and at external applied DC magnetic fields up to 0.9 T. Measurements of a high
purity sapphire cooled close to 100 mK reveal the presence of Fe,
Cr, and V impurities. A host of electron transitions are measured
and identified, including the two-photon classically forbidden quadrupole
transition () for Fe, as well as hyperfine transitions of
V
Determination of the Anisotropy of Permittivity of Quantum Paraelectric Strontium Titanate
The dielectric properties of strontium titanate (SrTiO) have previously
been reported from room temperature to low temperatures with conflicting
results. In this work, precision measurement of the permittivity is undertaken
by simultaneously measuring transverse electric and transverse magnetic
resonant modes within a single crystal. It is unequivocally shown that the
permittivity is isotropic at room temperature with a permittivity of order
by measuring multiple modes of different electric field
polarisations. As the crystal is cooled to 5 K and undergoes well known phase
transitions, we show the material becomes uniaxial anisotropic with the ratio
of the parallel to perpendicular permittivity to the cylinder z-axis of the
sample as high as 2.4 below 6 K
Strong Coupling Between P1 Diamond Impurity Centres and 3D Lumped Photonic Microwave Cavity
We report strong coupling between an ensemble of N impurity (P1) centres in
diamond and microwave photons using a unique double post re-entrant cavity. The
cavity is designed so that the magnetic component of the cavity field is
spatially separated from the electric component and focused into the small
volume in which the diamond sample is mounted. The novelty of the structure
simultaneously allows high magnetic filling factor (38.4\%) and low frequencies
necessary to interact, at low magnetic field, with transitions in diamond such
as those in NV and P1 centres. Coupling strength (or normal-mode
splitting) of 51.42 MHz, was achieved with P1 centres at 6.18 GHz and 220 mT in
a centimetre-scale cavity, with a corresponding cooperativity factor of 4.7.
This technique offers an alternative way, with some significant advantages, to
couple 3D cavities to transitions in diamond and achieve the strong coupling
necessary for applications to quantum information processing
Quartz-superconductor quantum electromechanical system
We propose and analyse a quantum electromechanical system composed of a
monolithic quartz bulk acoustic wave (BAW) oscillator coupled to a
superconducting transmon qubit via an intermediate LC electrical circuit.
Monolithic quartz oscillators offer unprecedentedly high effective masses and
quality factors for the investigation of mechanical oscillators in the quantum
regime. Ground-state cooling of such mechanical modes via resonant
piezoelectric coupling to an LC circuit, which is itself sideband cooled via
coupling to a transmon qubit, is shown to be feasible. The fluorescence
spectrum of the qubit, containing motional sideband contributions due to the
couplings to the oscillator modes, is obtained and the imprint of the
electromechanical steady-state on the spectrum is determined. This allows the
qubit to function both as a cooling resource for, and transducer of, the
mechanical oscillator. The results described are relevant to any hybrid quantum
system composed of a qubit coupled to two (coupled or uncoupled) thermal
oscillator modes.Comment: 19 pages, 3 figure
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