13 research outputs found
High Resolution Spectroscopy of Erbium Doped Solids
This thesis investigates the potential of Er:YSO and Er:Si for
quantum communication and computation applications. Erbium
uniquely possess optical transitions in the 1.5 um region, making
it suitable for both fibre telecommunication and silicon
photonics.
The properties of the
optical transition in Er:YSO have already been extensively
studied. Over two decades ago, improvements in
dephasing time at 1.5 um were achieved by applying a 5T field
along the D1 axis. More recently, a record 4.4 ms coherence time
on the same optical transition was achieved using a 7T field.
These investigations, among others, illustrate that large Er
electron spins become thermally polarised with sufficient
magnetic field. However, no long lived and coherent spin
transitions associated with the Er ions had previously been
identified, and such transitions are necessary for on-demand
quantum state storage.
To address this requirement, the optical and hyperfine transition
properties of 167-Er:YSO were investigated in large magnetic
fields. In a field of 7T, spectral hole lifetimes of 1 minute and
hyperfine population lifetimes of 12 minutes were observed. These
measurements illustrate the effect of spin-lattice relaxation in
this system, and how it can be mitigated.
Efficient spin-polarisation of the entire 167-Er hyperfine
ensemble is also demonstrated. This is the first such
demonstration in rare earth systems, and a key requirement for
broadband optical storage. Moreover, a 1.3 second coherence time
was recorded for an 167-Er:YSO hyperfine transition at 7T and 1.4
K. This is an improvement of several orders-of-magnitude over
previous coherence measurements on spin-transitions in Er doped
solids. This is also sufficient for maximal entanglement rates in
quantum repeater networks that span distances of 1000 km or
greater.
With an optical transition at 1.5 um, Er is also an ideal
candidate to connect silicon based quantum computers to the
future quantum Internet. In particular, single Er:Si ions could
be used to develop an optical-spin bus between P:Si qubits and
fibre based quantum networks.
Presented here is the first spectroscopic investigation of single
Er:Si ions. This required a novel opto-electronic approach to
single ion detection, where the Er ions are implanted into a
nanometre scale fin-shaped Field Effect Transistor. With this
approach it was possible to develop high resolution optical
spectra, where both the electronic and hyperfine levels of
individual Er ions were resolved.
Long optical and spin coherence times are also important
requirements for an optical-spin bus. To address the first
requirement, an investigation of the optical lineshape was
undertaken. Here it was determined that sources of Stark noise
external to the transistor channel contribute a significant
amount to optical homogeneous linewidth. However, the dominant
noise contribution was determined to be short-range (from within
the 30 nm wide channel) and the total homogeneous linewidth was
measured to be 50 MHz.
The site structure of an individual Er:Si ion was then analysed,
using magnetic field rotation patterns and optical transitions
between multiple crystal field levels. This site was determined
to have approximately axial () symmetry. The purpose of
this study was to determine a magnetic field regime in which the
Er electrons spin can be polarised, which is necessary for
realising of long hyperfine lifetimes and coherence times
Spatial mode storage in a gradient echo memory
Three-level atomic gradient echo memory (lambda-GEM) is a proposed candidate
for efficient quantum storage and for linear optical quantum computation with
time-bin multiplexing. In this paper we investigate the spatial multimode
properties of a lambda-GEM system. Using a high-speed triggered CCD, we
demonstrate the storage of complex spatial modes and images. We also present an
in-principle demonstration of spatial multiplexing by showing selective recall
of spatial elements of a stored spin wave. Using our measurements, we consider
the effect of diffusion within the atomic vapour and investigate its role in
spatial decoherence. Our measurements allow us to quantify the spatial
distortion due to both diffusion and inhomogeneous control field scattering and
compare these to theoretical models.Comment: 11 pages, 9 figure
Optical addressing of an individual erbium ion in silicon
The detection of electron spins associated with single defects in solids is a
critical operation for a range of quantum information and measurement
applications currently under development. To date, it has only been
accomplished for two centres in crystalline solids: phosphorus in silicon using
electrical readout based on a single electron transistor (SET) and
nitrogen-vacancy centres in diamond using optical readout. A spin readout
fidelity of about 90% has been demonstrated with both electrical readout and
optical readout, however, the thermal limitations of the electrical readout and
the poor photon collection efficiency of the optical readout hinder achieving
the high fidelity required for quantum information applications. Here we
demonstrate a hybrid approach using optical excitation to change the charge
state of the defect centre in a silicon-based SET, conditional on its spin
state, and then detecting this change electrically. The optical frequency
addressing in high spectral resolution conquers the thermal broadening
limitation of the previous electrical readout and charge sensing avoids the
difficulties of efficient photon collection. This is done with erbium in
silicon and has the potential to enable new architectures for quantum
information processing devices and to dramatically increase the range of defect
centres that can be exploited. Further, the efficient electrical detection of
the optical excitation of single sites in silicon is a major step in developing
an interconnect between silicon and optical based quantum computing
technologies.Comment: Corrected the third affiliation. Corrected one cross-reference of
"Fig. 3b" to "Fig. 3c". Corrected the caption of Fig. 3a by changing (+-)1 to
Single rare-earth ions as atomic-scale probes in ultra-scaled transistors
Continued dimensional scaling of semiconductor devices has driven information
technology into vastly diverse applications. As the size of devices approaches
fundamental limits, metrology techniques with nanometre resolution and
three-dimensional (3D) capabilities are desired for device optimisation. For
example, the performance of an ultra-scaled transistor can be strongly
influenced by the local electric field and strain. Here we study the spectral
response of single erbium ions to applied electric field and strain in a
silicon ultra-scaled transistor. Stark shifts induced by both the overall
electric field and the local charge environment are observed. Further, changes
in strain smaller than are detected, which is around two
orders of magnitude more sensitive than the standard techniques used in the
semiconductor industry. These results open new possibilities for
non-destructive 3D mapping of the local strain and electric field in the
channel of ultra-scaled transistors, using the single erbium ions as
ultra-sensitive atomic probes.Comment: 10+5 pages, 4+3 figure
Coherence time of over a second in a telecom-compatible quantum memory storage material
Quantum memories for light will be essential elements in future long-range quantum communication networks. These memories operate by reversibly mapping the quantum state of light onto the quantum transitions of a material system. For networks, the quantum coherence times of these transitions must be long compared to the network transmission times, approximately 100 ms for a global communication network. Due to a lack of a suitable storage material, a quantum memory that operates in the 1,550nm optical fibre communication band with a storage time greater than 1 mu s has not been demonstrated. Here we describe the spin dynamics of Er-167(3+):Y2SiO5 in a high magnetic field and demonstrate that this material has the characteristics for a practical quantum memory in the 1,550nm communication band. We observe a hyperfine coherence time of 1.3 s. We also demonstrate efficient spin pumping of the entire ensemble into a single hyperfine state, a requirement for broadband spin-wave storage. With an absorption of 70 dB cm(-1) at 1,538 nm and Lambda transitions enabling spin-wave storage, this material is the first candidate identified for an efficient, broadband quantum memory at telecommunication wavelengths
Parkes Weber syndrome-diagnostic and management paradigms: a systematic review
Objectives Parkes Weber syndrome is a congenital vascular malformation which consists of capillary malformation, venous malformation, lymphatic malformation, and arteriovenous malformation. Although Parkes Weber syndrome is a clinically distinctive entity with serious complications, it is still frequently misdiagnosed as Klippel-Trenaunay syndrome that consists of the triad capillary malformation, venous malformation, and lymphatic malformation. Methods We performed a systematic review investigating clinical, diagnostic, and treatment modalities of Parkes Weber syndrome (PubMed/MEDLINE, Embase, and Cochrane databases). Thirty-six publications (48 patients) fulfilled the eligibility criteria. Results The median age of patients was 23 years (IQR, 8-32), and 24 (50.0%) were males. Lower extremity was affected in 42 (87.5%) and upper extremity in 6 (12.5%) patients; 15 (31.3%) patients developed high-output heart failure; 12 (25.0%) patients had chronic venous ulcerations, whereas 4 (8.3%) manifested distal arterial ischemia. The spinal arteriovenous malformations were reported in six (12.5%) patients and coexistence of aneurysmatic disease in five (10.4%) patients. The most frequently utilized invasive treatments were embotherapy followed by amputation and surgical arteriovenous malformation resection, and occasionally stent-graft implantation. All modalities showed clinical improvement. However, long follow-up and outcome remained unclear. Conclusion A diagnosis of Parkes Weber syndrome should be made on the presence of capillary malformation, venous malformation, lymphatic malformation, and arteriovenous malformation (as main defect) in overgrowth extremity. Arteriovenous malformation presents the criterion for distinguishing Parkes Weber syndrome from Klippel-Trenaunay syndrome, which is substantial for treatment strategy. The primary management goal should be patient's quality of life improvement and complication reduction. Embolization alone/combined with surgical resection targeting occlusion or removal of arteriovenous malformation "nidus" reliably leads to clinical improvement
Assessing the potential of para-donor and para-acceptor substituted 5-benzylidenebarbituric acid derivatives as push-pull electronic systems: Experimental and quantum chemical study
Electronic interactions in donor-pi-linker-acceptor systems with barbituric acid as an electron acceptor and possible electron donor were investigated to screen promising candidates with a push-pull character based on experimental and quantum chemical studies. The tautomeric properties of 5-benzylidenebarbituric acid derivatives were studied with NMR spectra, spectrophotometric determination of the pKa values, and quantum chemical calculations. Linear solvation energy relationships (LSER) and linear free energy relationships (LFER) were applied to the spectral data - UV frequencies and C-13 NMR chemical shifts. The experimental studies of the nature of the ground and excited state of investigated compounds were successfully interpreted using a computational chemistry approach including ab initio MP2 geometry optimization and time-dependent DFT calculations of excited states. Quantification of the push-pull character of barbituric acid derivatives was performed by the (CNMR)-C-13 chemical shift differences, Mayer pi bond order analysis, hole-electron distribution analysis, and calculations of intramolecular charge transfer (ICT) indices. The results obtained show, that when coupled with a strong electron-donor, barbituric acid can act as the electron-acceptor in push-pull systems, and when coupled with a strong electron-acceptor, barbituric acid can act as the weak electron-donor
Spatial-mode storage in a gradient-echo memory
Three-level atomic gradient echo memory (Λ-GEM) is a proposed candidate for efficient quantum storage and for linear optical quantum computation with time-bin multiplexing. In this paper we investigate the spatial multimode properties of a Λ-GEM system