Name: generation and coherent control of pulsed quantum frequency combs
Uploaded: 2018-06-08T13:00:00
Description: Watch this Scientific Journal Video about Generation and Coherent Control of Pulsed Quantum Frequency Combs at JoVE.com

We thank R. Helsten for technical insights; P. Kung from QPS Photronics for the help and processing equipment; as well as QuantumOpus and N. Bertone of OptoElectronics Components for their support and for providing us with state-of-the-art photon detection equipment. This work was made possible by the following funding sources: Natural Sciences and Engineering Research Council of Canada (NSERC) (Steacie, Strategic, Discovery, and Acceleration Grants Schemes, Vanier Canada Graduate Scholarships, USRA Scholarship); Mitacs (IT06530) and PBEEE (207748); MESI PSR-SIIRI Initiative; Canada Research Chair Program; Australian Research Council Discovery Projects (DP150104327); European Union&#39;s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant (656607); CityU SRG-Fd program (7004189); Strategic Priority Research Program of the Chinese Academy of Sciences (XDB24030300); People Programme (Marie Curie Actions) of the European Union&#39;s FP7 Programme under REA grant agreement INCIPIT (PIOF-GA-2013-625466); Government of the Russian Federation through the ITMO Fellowship and Professorship Program (Grant 074-U 01); 1000 Talents Sichuan Program (China)

1. Generation of the High-dimensional Frequency-bin Entangled States via Pulsed Excitation
<ol>
	<li>Following the scheme outlined in Figure 2 (Generation stage), connect each component using polarization-maintaining optical fibers (for improved environmental stability).</li>
	<li>Connect a power supply to the electro-optic amplitude modulator and apply a DC voltage offset, tuning the offset value until the optical power transmitted through it is approximately halved (measured using an opt...

<ol>
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The optical frequency-domain, via QFCs, is advantageous in quantum applications for a host of reasons. Operations are global, acting on all states simultaneously, which results in a design that does not scale in size or complexity as the state dimensionality increases. This is enhanced as the components can be reconfigured on-the-fly without changing the setup and are capable of being integrated on-chip by exploiting existing and/or developing semiconductor and telecommunications infrastructures. The generation technique...

The control of quantum phenomena opens the possibility for new applications in fields as diverse as secure quantum communications1, powerful quantum information processing2, and quantum sensing3. While a variety of physical platforms are actively being researched for the realizations of quantum technologies4, optical quantum states are important candidates as they can exhibit long coherence times and stability from external noise, excellent transmission properties, as well as compatibility with existing telecommunications and silicon chip (CMOS) technologies.
Towards fully realizing the potential of photons for quantum technologies, state complexity and information content can be increased through the use of multiple entangled parties and/or high-dimensionality. However, the on-chip generation of such optical states lacks practicality as setups are complicated, not perfectly scalable, and/or use highly-specialized components. Specifically, high-dimensional path-entanglement requires <img alt="Equation 01" src="/files/ftp_upload/57517/57517eq01v3.jpg" /> coherently-excited identical sources and elaborate circuits of beam-splitters5 (where <img alt="Equation 01" src="/files/ftp_upload/57517/57517eq01v3.jpg" /> is the state dimensionality), while time-entanglement needs complex multi-arm interferometers6. Remarkably, the frequency-domain is well-suited for the scalable generation and control of complex states, as shown by its recent exploitation in quantum frequency combs (QFC)7,8 using a combination of integrated optics and telecommunication infrastructures9, and provides a promising framework for future quantum information technologies.
On-chip QFCs are generated using nonlinear optical effects in integrated micro-cavities. Using such a nonlinear micro-resonator, two entangled photons (noted as signal and idler) are produced by spontaneous four-wave mixing, via the annihilation of two excitation photons - with the resultant pair generated in a superposition of the cavity&#39;s evenly-spaced resonant frequency modes (Figure 1). If there is coherence between the individual frequency modes, a frequency-bin entangled state is formed10, which is often referred to as a mode-locked two photon state11. This state wave-function can be described by,
<img alt="Equation 02" src="/files/ftp_upload/57517/57517eq02v3.jpg" />
Here, <img alt="Equation 03" src="/files/ftp_upload/57517/57517eq03v3.jpg" /> and <img alt="Equation 04" src="/files/ftp_upload/57517/57517eq04v3.jpg" /> are the single-frequency-mode idler and signal components, respectively, and <img alt="Equation 05" src="/files/ftp_upload/57517/57517eq05v3.jpg" /> is the probability amplitude for the <img alt="Equation 06" src="/files/ftp_upload/57517/57517eq06v3.jpg" />-th signal-idler mode pair.
Previous demonstrations of on-chip QFCs highlight their versatility as viable quantum information platforms, and include combs of correlated photons12, cross-polarized photons13, entangled photons14,15,16, multi-photon states15, and frequency-bin entangled states9,17. Here, we provide a detailed overview of the QFC platform and a protocol for high-dimensional frequency-bin entangled optical state generation and control.
Future quantum applications, especially those to be interfaced with high-speed electronics (for timely information processing), demand the high-rate generation of high-purity photon states in a compact and stable setup. We use an actively mode-locked, nested cavity scheme to produce QFCs within the telecommunications S, C, and L frequency bands. A micro-ring is incorporated into a larger pulsed laser cavity, with optical gain (provided by an erbium-doped fiber amplifier, EDFA) filtered to match the micro-ring excitation bandwidth18. Mode-locking is actively realized via electro-optic modulation of the cavity losses19. An isolator ensures that pulse propagation follows a single direction. The resulting pulse train has very low root mean square (RMS) noise and exhibits tunable repetition rates and pulse powers. A high isolation notch filter separates the emitted QFC photons from the excitation field. These single photons are then guided through fibers for control and detection.
Our scheme is a step towards a high generation-rate, small-footprint QFC source, as all components used can potentially be integrated onto a photonic chip. Additionally, pulsed excitation is particularly well-suited for quantum applications. First, looking at a pair of micro-cavity resonances symmetric to the excitation, it generates two-photon states where each photon is characterized by a single-frequency mode&#8211; central for linear optical quantum computing20. As well, multi-photon states can be generated by moving to higher power excitation regimes and selecting multiple signal-idler pairs15. Second, as photons are emitted in known time windows corresponding to the pulsed excitation, post-processing and gating can be implemented to improve state detection. Perhaps most significantly, our scheme supports high generation rates of photon states using harmonic mode-locking without reducing the coincidence-to-accidental ratio (CAR) &#8211; which could pave the way for high-speed, multi-channel quantum information technologies.
To demonstrate the impact and feasibility of the frequency-domain, control of QFC states must be accomplished in targeted ways, ensuring highly efficient transformations and state coherence. To satisfy such requirements, we use cascaded programmable filters and phase modulators &#8211; established components in the telecommunications industry. Programmable filters can be used to impose an arbitrary spectral amplitude and phase mask on the single photons, with a resolution sufficient to address each frequency mode individually; and electro-optic phase modulators driven by radio-frequency (RF) signal generators facilitate the mixing of frequency components21.
The most important aspect of this control scheme is that it operates on all quantum modes of the photons simultaneously in a single spatial mode, using single control elements. Increasing the quantum state dimensionality will not lead to an increase in the setup complexity, in contrast to path- or time-bin entanglement schemes. As well, all components are externally reconfigurable (meaning the operations can be altered without amending the setup) and use existing telecommunications infrastructure. Thus, existing and upcoming developments in the field of ultrafast optical processing can be directly transferred to the scalable control of quantum states in the future.
In summary, the exploitation of the frequency-domain by QFCs supports the high-rate generation of complex quantum states and their control, and, is thus well-suited for the harnessing of complex states towards practical and scalable quantum technologies.

<table>
	<tbody>
		<tr>
			<td>Superconducting Nanowire Single-Photon Detector System</td>
			<td>Quantum Opus</td>
			<td>Opus One</td>
			<td></td>
		</tr>
		<tr>
			<td>Electro-optic phase modulator</td>
			<td>EO-Space</td>
			<td>Low loss model</td>
			<td></td>
		</tr>
		<tr>
			<td>Programmable filter</td>
			<td>Finisar&#160;</td>
			<td>WaveShaper 4000s</td>
			<td></td>
		</tr>
		<tr>
			<td>Timing electronics</td>
			<td>PicoQuant</td>
			<td>HydraHarp 400</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro-ring resonator</td>
			<td></td>
			<td></td>
			<td>200 GHz FSR micro-ring resonator made from high refractive index glass. See Ref. 24 for platform details.</td>
		</tr>
		<tr>
			<td>Erbium-doped fiber amplifier</td>
			<td>Keopsys</td>
			<td>PEFA-SP-C-PM-27-B202-FA-FA</td>
			<td></td>
		</tr>
		<tr>
			<td>Electro-optic amplitude modulator</td>
			<td>Oclaro&#160;</td>
			<td>SD40</td>
			<td></td>
		</tr>
		<tr>
			<td>RF tone source</td>
			<td>Rohde &#38; Schwarz</td>
			<td>SMP 04</td>
			<td></td>
		</tr>
		<tr>
			<td>RF tone amplifier</td>
			<td>RF-Lambda</td>
			<td>RFLUPA27G34GA</td>
			<td></td>
		</tr>
		<tr>
			<td>Function generator</td>
			<td>Tetronix</td>
			<td>AFG 3251</td>
			<td></td>
		</tr>
		<tr>
			<td>Isolator</td>
			<td>General Photonics</td>
			<td>NISO-S-15-SS-FC/APF</td>
			<td></td>
		</tr>
		<tr>
			<td>Oscilloscope</td>
			<td>Tetronix&#160;</td>
			<td>TDS5052B</td>
			<td></td>
		</tr>
		<tr>
			<td>Photodiode</td>
			<td>Finisar</td>
			<td>XPDV 50 GHz</td>
			<td></td>
		</tr>
		<tr>
			<td>DWDM</td>
			<td>OptiWorks</td>
			<td>DWFUQUMD08BN</td>
			<td></td>
		</tr>
		<tr>
			<td>Power supply</td>
			<td>Madell</td>
			<td>CA18303D</td>
			<td></td>
		</tr>
	</tbody>
</table>

generation and coherent control of pulsed quantum frequency combs

We present a method for the generation and coherent manipulation of pulsed quantum frequency combs. Until now, methods of preparing high-dimensional states on-chip in a practical way have remained elusive due to the increasing complexity of the quantum circuitry needed to prepare and process such states. Here, we outline how high-dimensional, frequency-bin entangled, two-photon states can be generated at a stable, high generation rate by using a nested-cavity, actively mode-locked excitation of a nonlinear micro-cavity. This technique is used to produce pulsed quantum frequency combs. Moreover, we present how the quantum states can be coherently manipulated using standard telecommunications components such as programmable filters and electro-optic modulators. In particular, we show in detail how to accomplish state characterization measurements such as density matrix reconstruction, coincidence detection, and single photon spectrum determination. The presented methods form an accessible, reconfigurable, and scalable foundation for complex high-dimensional state preparation and manipulation protocols in the frequency domain.

The outlined scheme for the generation and control of high-dimensional frequency-bin states (based on the excitation of nonlinear micro-cavities, Figure 1) is shown in Figure 2. This setup uses standard telecommunications components and is highly flexible in the photon production rate and the processing operations applied. Figure 3 shows the characterization of the generation scheme through the coinc...

Watch this Scientific Journal Video about Generation and Coherent Control of Pulsed Quantum Frequency Combs at JoVE.com

Generation and Coherent Control of Pulsed Quantum Frequency Combs

A protocol is presented for the practical generation and coherent manipulation of high-dimensional frequency-bin entangled photon states using integrated micro-cavities and standard telecommunications components, respectively.

We present a method for the generation and coherent manipulation of pulsed quantum frequency combs. Until now, methods of preparing high-dimensional ...

The overall goal of this protocol is to generate and coherently control pulsed quantum frequency combs which may be used for quantum information processing. This method can help us provide the tools for fundamental investigations of quantum mechanics and for realizing non-classical technologies, such as quantum communications and information processing. The main advantage of this technique is that well-established telecommunications components and protocols are used to generate and control complex optical quantum states in a reconfigurable and scalable way.We have this idea when we talk with my colleague Jose Azana who is an expert in telecommunication processing, and we realized that we could transfer these tools to the world of quantum objects. Set up the components of the system on an optical table. The system has stages for generation, control, and processing.This depiction provides an overview. All elements are connected with polarization maintaining optical fiber. For now, focus on the generation stage.This stage features an on chip micro-ring resonator embedded in a larger external cavity. The external cavity is made of an electro-optic amplitude modulator driven by a signal generator, an isolator, and an erbium-doped fiber amplifier providing optical gain. There is a narrow filter with a pass band selecting a single microcavity resonance and a notch filter routing the generated photons to the control section.With the cavity disconnected, initiate the erbium-doped fiber amplifier. Use an optical power meter after the amplitude modulator to measure the transmitted power. At the modulator, use a power supply to apply a DC offset to have the transmitted power.Reconnect the cavity and insert a fast photo diode into a different ring port. Use an oscilloscope to observe its signal in the time domain. Without the modulator activated, the output will show unstable pulse operation with a low quality pulse train.Return to the amplitude modulator and connect the function generator. Set the output frequency of the generator to a multiple of the approximate external cavity mode spacing. Selecting a rectangular or sine waveform and turn on the function generator.Tune the function generator frequency and DC offset to optimize and stabilize the pulse train on the oscilloscope. Manually adjust the gain to set the pulse intensity. The non-linear four wave mixing process inside the ring resonator now creates signal and idler photon pairs which will leave the external cavity at the notch filter.Connect the synchronization signal from the function generator to the timing electronics. The generation rate of this pulsed quantum frequency comb may be increased by driving the modulator a higher harmonics of the external cavity frequency spacing, thus entering a harmonic mode locking machine. The amplifier gain must then also be increased to ensure the same power per pulse.After the notch filter in the generation stage, the entangled photons enter the control stage. There, in order, they encounter a programmable filter, a phase modulator, and a second programmable filter. First, program the filters.Set the amplitude of the desired frequency mode channels and attenuate the others. Similarly, decide on the desired phase mask. Do this for each filter.This image represents the amplitude and phase for a coincidence measurement. To prepare the phase modulator, connect the signal generator to the RF amplifier with low loss cables. Then connect the RF amplifier to the phase modulator.Once all the RF ends are connected and terminated, bias the amplifier. Set the RF signal generator to create sidebands which overlap with the desired frequency modes, then turn it on. As a test, set up the system to send a continuous wave laser beam through the phase modulator.Use an optical spectrum analyzer to check that the input spectrum produces an output spectrum that corresponds to the intended modulation for the experiment. To continue, connect the phase modulator with the programmable filters. When setting the phase modulation pattern, it is important to determine what pattern will create the targeted frequency sidebands for the chosen operation.This will depend on the dimension of the quantum state used and on microcavity resonance spacing. The photon pairs from the generation stage enter the control stage. The first filter sets the programmed amplitude and phase.Next, the phase modulator creates the necessary frequency sidebands. The second filter selects the signal and idler pair. On input to the processing stage, separate the entangled photons with a dense wavelength division multiplexer.From there, they each go to single photon detectors. Record the arrival time of each photon using timing electronics set up for coincidence measurement. The setup allows coherent control over the photon states.Here frequency sidebands are generated via phase modulation. The sideband spacing and amplitudes are determined by the modulating signal. Coherent control of the photon state can be used for quantum state tomography.This is an example reconstruction of the state density matrix for a two photon system with a dimensionality of three for each photon. The fidelity between the measured and maximally entangled states is about 81%The pulsed high repetition rate generation technique is not limited to micro-ring resonators and may be adopted for other optical cavities, such as photonic crystal waveguides, microdisks, and second-order nonlinear cavities. With its development, the platform combines established techniques in telecommunications with quantum technologies towards potential applications, like secure communications at high rates over multiplex channels or high-dimensional quantum operations.

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Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Gradient Echo Quantum Memory in Warm Atomic Vapor

Gradient echo memory (GEM) is a protocol for storing optical quantum states of light in atomic ensembles. The primary motivation for such a technology is that quantum key distribution (QKD), which uses Heisenberg uncertainty to guarantee security of cryptographic keys, is limited in transmission distance. The development of a quantum repeater is a possible path to extend QKD range, but a repeater will need a quantum memory. In our experiments we use a gas of rubidium 87 vapor that is contained in a warm gas cell. This makes the scheme particularly simple. It is also a highly versatile scheme that enables in-memory refinement of the stored state, such as frequency shifting and bandwidth manipulation. The basis of the GEM protocol is to absorb the light into an ensemble of atoms that has been prepared in a magnetic field gradient. The reversal of this gradient leads to rephasing of the atomic polarization and thus recall of the stored optical state. We will outline how we prepare the atoms and this gradient and also describe some of the pitfalls that need to be avoided, in particular four-wave mixing, which can give rise to optical gain.

The gradient echo memory is a protocol for storing optical quantum states of light in atomic ensembles. Quantum memory is a key element of a quantum repeater, which can extend the range of quantum key distribution. We outline the operation of the scheme when implemented in a 3-level atomic ensemble.

Gradient  echo memory (GEM) is a protocol for storing optical quantum states of light in  atomic ensembles. The primary motivation for such a technology ...

Nanofabrication of Gate-defined GaAs/AlGaAs Lateral Quantum Dots

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and entanglement, to solve certain problems exponentially faster than with the best known algorithms on a classical computer. Gate-defined lateral quantum dots on GaAs/AlGaAs are one of many avenues explored for the implementation of a qubit. When properly fabricated, such a device is able to trap a small number of electrons in a certain region of space. The spin states of these electrons can then be used to implement the logical 0 and 1 of the quantum bit. Given the nanometer scale of these quantum dots, cleanroom facilities offering specialized equipment- such as scanning electron microscopes and e-beam evaporators- are required for their fabrication. Great care must be taken throughout the fabrication process to maintain cleanliness of the sample surface and to avoid damaging the fragile gates of the structure. This paper presents the detailed fabrication protocol of gate-defined lateral quantum dots from the wafer to a working device. Characterization methods and representative results are also briefly discussed. Although this paper concentrates on double quantum dots, the fabrication process remains the same for single or triple dots or even arrays of quantum dots. Moreover, the protocol can be adapted to fabricate lateral quantum dots on other substrates, such as Si/SiGe.

This paper presents a detailed fabrication protocol for gate-defined semiconductor lateral quantum dots on gallium arsenide heterostructures. These nanoscale devices are used to trap few electrons for use as quantum bits in quantum information processing or for other mesoscopic experiments such as coherent conductance measurements.

A quantum computer is a computer composed of quantum bits (qubits) that takes advantage of quantum effects, such as superposition of states and ...

Analysis of Contact Interfaces for Single GaN Nanowire Devices

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit a strong degradation after annealing due to the occurrence of void formation at the contact/SiO2 interface. This void formation can cause cracking and delamination of the metal film, which can increase the resistance or lead to a complete failure of the NW device. In order to address issues associated with void formation, a technique was developed that removes Ni/Au contact metal films from the substrates to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN NW devices. This procedure determines the degree of adhesion of the contact films to the substrate and NWs and allows for the characterization of the morphology and composition of the contact interface with the substrate and nanowires. This technique is also useful for assessing the amount of residual contamination that remains from the NW suspension and from photolithographic processes on the NW-SiO2 surface prior to metal deposition. The detailed steps of this procedure are presented for the removal of annealed Ni/Au contacts to Mg-doped GaN NWs on a SiO2 substrate.

A technique was developed that removes Ni/Au contact metal films from their substrate to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN nanowire devices.

Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit  a strong degradation after annealing due to the  occurrence of void formation at the ...

Construction and Characterization of External Cavity Diode Lasers for Atomic Physics

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs1,2. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling1,2 makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman3, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included.

This is an instructional paper to guide the construction and diagnostics of external cavity diode lasers (ECDLs), including component selection and optical alignment, as well as the basics of frequency reference spectroscopy and laser linewidth measurements for applications in the field of atomic physics.

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and ...

Coherent anti-Stokes Raman Scattering (CARS) Microscopy Visualizes Pharmaceutical Tablets During Dissolution

Traditional pharmaceutical dissolution tests determine the amount of drug dissolved over time by measuring drug content in the dissolution medium. This method provides little direct information about what is happening on the surface of the dissolving tablet. As the tablet surface composition and structure can change during dissolution, it is essential to monitor it during dissolution testing. In this work coherent anti-Stokes Raman scattering microscopy is used to image the surface of tablets during dissolution while UV absorption spectroscopy is simultaneously providing inline analysis of dissolved drug concentration for tablets containing a 50% mixture of theophylline anhydrate and ethyl cellulose. The measurements showed that in situ CARS microscopy is capable of imaging selectively theophylline in the presence of ethyl cellulose. Additionally, the theophylline anhydrate converted to theophylline monohydrate during dissolution, with needle-shaped crystals growing on the tablet surface during dissolution. The conversion of theophylline anhydrate to monohydrate, combined with reduced exposure of the drug to the flowing dissolution medium resulted in decreased dissolution rates. Our results show that in situ CARS microscopy combined with inline UV absorption spectroscopy is capable of monitoring pharmaceutical tablet dissolution and correlating surface changes with changes in dissolution rate.

Coherent anti-Stokes Raman Scattering CARS Microscopy Visualizes Pharmaceutical Tablets During Dissolution

Coherent anti-Stokes Raman scattering (CARS) microscopy is combined with an intrinsic flow-through dissolution setup to allow in situ and real-time visualization of the surface of pharmaceutical tablets undergoing dissolution. Using this custom-built setup, it is possible to correlate CARS videos with drug dissolution profiles recorded using inline UV absorption spectroscopy.

Traditional pharmaceutical dissolution tests determine the amount of drug dissolved over time by measuring drug content in the dissolution medium. This ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

Silicon Metal-oxide-semiconductor Quantum Dots for Single-electron Pumping

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by quantum mechanical effects such as tunneling through single dopants, scattering via interface defects, and discrete trap charge states. However, progress in silicon technology has shown that these phenomena can be harnessed and exploited for a new class of quantum-based electronics. Among others, multi-layer-gated silicon metal-oxide-semiconductor (MOS) technology can be used to control single charge or spin confined in electrostatically-defined quantum dots (QD). These QD-based devices are an excellent platform for quantum computing applications and, recently, it has been demonstrated that they can also be used as single-electron pumps, which are accurate sources of quantized current for metrological purposes. Here, we discuss in detail the fabrication protocol for silicon MOS QDs which is relevant to both quantum computing and quantum metrology applications. Moreover, we describe characterization methods to test the integrity of the devices after fabrication. Finally, we give a brief description of the measurement set-up used for charge pumping experiments and show representative results of electric current quantization.

The fabrication process and experimental characterization techniques relevant to single-electron pumps based on silicon metal-oxide-semiconductor quantum dots are discussed.

As mass-produced silicon transistors have reached the nano-scale, their behavior and performances are increasingly affected, and often deteriorated, by ...

Study of Siphon Breaker Experiment and Simulation for a Research Reactor

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent this outflow, a control device is required. A siphon breaker is a type of safety device that can be utilized to control the loss of coolant water effectively.
To analyze the characteristics of siphon breaking, a real-scale experiment was conducted. From the results of the experiment, it was found that there are several design factors that affect the siphon breaking phenomenon. Therefore, there is a need to develop a theoretical model capable of predicting and analyzing the siphon breaking phenomenon under various design conditions. Using the experimental data, it was possible to formulate a theoretical model that accurately predicts the progress and the result of the siphon breaking phenomenon. The established theoretical model is based on fluid mechanics and incorporates the Chisholm model to analyze two-phase flow. From Bernoulli&#39;s equation, the velocity, quantity, undershooting height, water level, pressure, friction coefficient, and factors related to the two-phase flow could be obtained or calculated. Moreover, to utilize the model established in this study, a siphon breaker analysis and design program was developed. The simulation program operates on the theoretical model basis and returns the result as a graph. The user can confirm the possibility of the siphon breaking by checking the shape of the graph. Furthermore, saving the entire simulation result is possible and it can be used as a resource for analyzing the real siphon breaking system.
In conclusion, the user can confirm the status of the siphon breaking and design the siphon breaker system using the program developed in this study.

The siphon breaking phenomenon was investigated experimentally and a theoretical model was proposed. A simulation program based on the theoretical model was developed and the results of the simulation program were compared with experimental results. It was concluded that the results of the simulation program matched the experimental results well.

Under the design conditions of a research reactor, the siphon phenomenon induced by pipe rupture can cause continuous outward flow of water. To prevent ...

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape method or individual WS2 nanotubes by dispersing the suspension of WS2 nanotubes. The selected samples have been fabricated into devices by the use of the electron beam lithography and electrolyte is put on the devices. We have characterized the electronic properties of the devices under applying the gate voltage. In the small gate voltage region, ions in the electrolyte are accumulated on the surface of the samples which leads to the large electric potential drop and resultant electrostatic carrier doping at the interface. Ambipolar transfer curve has been observed in this electrostatic doping region. When the gate voltage is further increased, we met another drastic increase of source-drain current which implies that ions are intercalated into layers of WS2 and electrochemical carrier doping is realized. In such electrochemical doping region, superconductivity has been observed. The focused technique provides a powerful strategy for achieving the electric-filed-induced quantum phase transition.

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

Here, we present a protocol to control the carrier number in solids by using the electrolyte.

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape ...