Publications by authors named "Hai-ou Li"

41 Publications

Ultrafast coherent control of a hole spin qubit in a germanium quantum dot.

Nat Commun 2022 Jan 11;13(1):206. Epub 2022 Jan 11.

CAS Key Laboratory of Quantum Information, University of Science and Technology of China, 230026, Hefei, Anhui, China.

Operation speed and coherence time are two core measures for the viability of a qubit. Strong spin-orbit interaction (SOI) and relatively weak hyperfine interaction make holes in germanium (Ge) intriguing candidates for spin qubits with rapid, all-electrical coherent control. Here we report ultrafast single-spin manipulation in a hole-based double quantum dot in a germanium hut wire (GHW). Mediated by the strong SOI, a Rabi frequency exceeding 540 MHz is observed at a magnetic field of 100 mT, setting a record for ultrafast spin qubit control in semiconductor systems. We demonstrate that the strong SOI of heavy holes (HHs) in our GHW, characterized by a very short spin-orbit length of 1.5 nm, enables the rapid gate operations we accomplish. Our results demonstrate the potential of ultrafast coherent control of hole spin qubits to meet the requirement of DiVincenzo's criteria for a scalable quantum information processor.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-021-27880-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8752786PMC
January 2022

An Operation Guide of Si-MOS Quantum Dots for Spin Qubits.

Nanomaterials (Basel) 2021 Sep 24;11(10). Epub 2021 Sep 24.

CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China.

In the last 20 years, silicon quantum dots have received considerable attention from academic and industrial communities for research on readout, manipulation, storage, near-neighbor and long-range coupling of spin qubits. In this paper, we introduce how to realize a single spin qubit from Si-MOS quantum dots. First, we introduce the structure of a typical Si-MOS quantum dot and the experimental setup. Then, we show the basic properties of the quantum dot, including charge stability diagram, orbital state, valley state, lever arm, electron temperature, tunneling rate and spin lifetime. After that, we introduce the two most commonly used methods for spin-to-charge conversion, i.e., Elzerman readout and Pauli spin blockade readout. Finally, we discuss the details of how to find the resonance frequency of spin qubits and show the result of coherent manipulation, i.e., Rabi oscillation. The above processes constitute an operation guide for helping the followers enter the field of spin qubits in Si-MOS quantum dots.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/nano11102486DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8540968PMC
September 2021

Anisotropic -Factor and Spin-Orbit Field in a Germanium Hut Wire Double Quantum Dot.

Nano Lett 2021 May 29;21(9):3835-3842. Epub 2021 Apr 29.

CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China.

Holes in nanowires have drawn significant attention in recent years because of the strong spin-orbit interaction, which plays an important role in constructing Majorana zero modes and manipulating spin-orbit qubits. Here, from the strongly anisotropic leakage current in the spin blockade regime for a double dot, we extract the full -tensor and find that the spin-orbit field is in plane with an azimuthal angle of 59° to the axis of the nanowire. The direction of the spin-orbit field indicates a strong spin-orbit interaction along the nanowire, which may have originated from the interface inversion asymmetry in Ge hut wires. We also demonstrate two different spin relaxation mechanisms for the holes in the Ge hut wire double dot: spin-flip co-tunneling to the leads, and spin-orbit interaction within the double dot. These results help establish feasibility of a Ge-based quantum processor.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.1c00263DOI Listing
May 2021

A Suspended Silicon Single-Hole Transistor as an Extremely Scaled Gigahertz Nanoelectromechanical Beam Resonator.

Adv Mater 2020 Dec 16;32(52):e2005625. Epub 2020 Nov 16.

CAS Key Laboratory of Quantum Information, CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui, 230026, China.

Suspended single-hole transistors (SHTs) can also serve as nanoelectromechanical resonators, providing an ideal platform for investigating interactions between mechanical vibrations and charge carriers. Demonstrating such a device in silicon (Si) is of particular interest, due to the strong piezoresistive effect of Si and potential applications in Si-based quantum computation. Here, a suspended Si SHT also acting as a nanoelectromechanical beam resonator is demonstrated. The resonant frequency and zero-point motion of the device are ≈3 GHz and 0.2 pm, respectively, reaching the best level among similar devices demonstrated with Si-containing materials. The mechanical vibration is transduced to electrical readout by the SHT. The signal transduction mechanism is dominated by the piezoresistive effect. A giant apparent effective piezoresistive gauge factor with strong correlation to single-hole tunneling is extracted in this device. The results show the great potential of the device in interfacing charge carriers with mechanical vibrations, as well as investigating potential quantum behavior of the vibration phonon mode.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/adma.202005625DOI Listing
December 2020

Tunable parametric amplification of a graphene nanomechanical resonator in the nonlinear regime.

Nanotechnology 2021 Apr;32(15):155203

CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.

Parametric amplification is widely used in nanoelectro-mechanical systems to enhance the transduced mechanical signals. Although parametric amplification has been studied in different mechanical resonator systems, the nonlinear dynamics involved receives less attention. Taking advantage of the excellent electrical and mechanical properties of graphene, we demonstrate electrical tunable parametric amplification using a doubly clamped graphene nanomechanical resonator. By applying external microwave pumping with twice the resonant frequency, we investigate parametric amplification in the nonlinear regime. We experimentally show that the extracted coefficient of the nonlinear Duffing force α and the nonlinear damping coefficient η vary as a function of external pumping power, indicating the influence of higher-order nonlinearity beyond the Duffing (∼x ) and van der Pol (∼[Formula: see text]) types in our device. Even when the higher-order nonlinearity is involved, parametric amplification still can be achieved in the nonlinear regime. The parametric gain increases and shows a tendency of saturation with increasing external pumping power. Further, the parametric gain can be electrically tuned by the gate voltage with a maximum gain of 10.2 dB achieved at the gate voltage of 19 V. Our results will benefit studies on nonlinear dynamics, especially nonlinear damping in graphene nanomechanical resonators that has been debated in the community over past decade.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1361-6528/abc9eaDOI Listing
April 2021

Narrow-band asymmetric transmission based on the dark mode of Fano resonance on symmetric trimeric metasurfaces.

Opt Express 2020 Sep;28(20):30141-30149

Asymmetric transmission (AT) is useful for polarization manipulation. We report narrowband AT that utilizes a triple-layered symmetric trimeric metasurface with near-field coupling of the dark mode of the Fano resonance. The coupling strength of the dark mode was tuned by using a mid-layer to break the dim AT between two slit layers. The peak transmission of linearly polarized waves and percentage bandwidth reached 0.7719 and 1.26% (numerical simulations) and 0.49 and 1.9% (experiments), respectively. Coupled-mode theory and field patterns are utilized to explain the underlying physical mechanisms of the mid-layer assisted field coupling. These results are useful for Fano-resonance-based devices.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.403281DOI Listing
September 2020

Identification of NEO1 as a prognostic biomarker and its effects on the progression of colorectal cancer.

Cancer Cell Int 2020 17;20:510. Epub 2020 Oct 17.

Department of Gastroenterology, Zhongnan Hospital of Wuhan University, No. 169, Donghu Road, Wuchang District, Wuhan, 430071 Hubei Province China.

Background: Due to the high morbidity and poor clinical outcomes, early predictive and prognostic biomarker identification is desiderated in colorectal cancer (CRC). As a homologue of the Deleted in Colorectal Cancer (DCC) gene, the role of Neogenin-1 (NEO1) in CRC remained unveiled. This study was designed to probe into the effects and potential function of NEO1 in CRC.

Methods: Online databases, Gene Set Enrichment Analysis (GSEA), quantitative real-time PCR and western blotting were used to evaluate NEO1 expression in colorectal cancer tissues. Survival analysis was performed to predict the prognosis of CRC patients based on NEO1 expression level. Then, cell proliferation was detected by colony formation and Cell Counting Kit 8 (CCK-8) assays. CRC cell migration and invasion were examined by transwell assays. Finally, we utilized the Gene Set Variation Analysis (GSVA) and GSEA to dig the potential mechanisms of NEO1 in CRC.

Results: Oncomine database and The Cancer Genome Atlas (TCGA) database showed that NEO1 was down-regulated in CRC. Further results validated that NEO1 mRNA and protein expression were both significantly lower in CRC tumor tissues than in the adjacent tissues in our clinical samples. NEO1 expression was decreased with the progression of CRC. Survival and other clinical characteristic analyses exhibited that low NEO1 expression was related with poor prognosis. A gain-of-function study showed that overexpression of NEO1 restrained proliferation, migration and invasion of CRC cells while a loss-of-function showed the opposite effects. Finally, functional pathway enrichment analysis revealed that NEO1 low expression samples were enriched in inflammation-related signaling pathways, EMT and angiogenesis.

Conclusion: A tumor suppressor gene NEO1 was identified and verified to be correlated with the prognosis and progression of CRC, which could serve as a prognostic biomarker for CRC patients.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12935-020-01604-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7568410PMC
October 2020

Giant Anisotropy of Spin Relaxation and Spin-Valley Mixing in a Silicon Quantum Dot.

Phys Rev Lett 2020 Jun;124(25):257701

CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China.

In silicon quantum dots (QDs), at a certain magnetic field commonly referred to as the "hot spot," the electron spin relaxation rate (T_{1}^{-1}) can be drastically enhanced due to strong spin-valley mixing. Here, we experimentally find that with a valley splitting of 78.2±1.6  μeV, this hot spot in spin relaxation can be suppressed by more than 2 orders of magnitude when the in-plane magnetic field is oriented at an optimal angle, about 9° from the [100] sample plane. This directional anisotropy exhibits a sinusoidal modulation with a 180° periodicity. We explain the magnitude and phase of this modulation using a model that accounts for both spin-valley mixing and intravalley spin-orbit mixing. The generality of this phenomenon is also confirmed by tuning the electric field and the valley splitting up to 268.5±0.7  μeV.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevLett.124.257701DOI Listing
June 2020

Identification of as the Hub Gene Associated with KRAS Mutation in Colorectal Cancer by Coexpression Analysis.

DNA Cell Biol 2020 Sep 16;39(9):1639-1648. Epub 2020 Jun 16.

Department of Gastroenterology, Zhongnan Hospital of Wuhan University, Wuhan, China.

Colorectal cancer (CRC) patients with KRAS mutation are refractory and usually have poor prognosis. We aimed to identify the hub gene associated with KRAS mutant CRCs. Weighted gene coexpression network analysis (WGCNA) was used to calculate the key module and the hub genes in GSE39582. Combined with the protein-protein interaction (PPI) network and survival analysis, the real hub gene was identified and further validated. With the highest module significance value and correlation coefficient, the blue module was selected as the key module, 19 genes were identified as the hub gene candidates. The above genes were significantly downregulated in KRAS mutant CRCs compared with the wild type. Four genes ( and ) were further screened as the potential hub genes by the PPI network. Low expression of for KRAS mutant patients had a poor prognosis. Therefore, was identified as the hub gene. expression was also downregulated in other two CRC datasets. "MAPK SIGNALING PATHWAY" was enriched in lowly expressed samples. was identified and validated to be closely related to KRAS mutation. It could be a potential prognosis biomarker and a novel treatment target for KRAS mutant CRC patients.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/dna.2020.5574DOI Listing
September 2020

Coherent phonon dynamics in spatially separated graphene mechanical resonators.

Proc Natl Acad Sci U S A 2020 Mar 2;117(11):5582-5587. Epub 2020 Mar 2.

Chinese Academy of Sciences Key Laboratory of Quantum Information, University of Science and Technology of China, 230026 Hefei, Anhui, China;

Vibrational modes in mechanical resonators provide a promising candidate to interface and manipulate classical and quantum information. The observation of coherent dynamics between distant mechanical resonators can be a key step toward scalable phonon-based applications. Here we report tunable coherent phonon dynamics with an architecture comprising three graphene mechanical resonators coupled in series, where all resonators can be manipulated by electrical signals on control gates. We demonstrate coherent Rabi oscillations between spatially separated resonators indirectly coupled via an intermediate resonator serving as a phonon cavity. The Rabi frequency fits well with the microwave burst power on the control gate. We also observe Ramsey interference, where the oscillation frequency corresponds to the indirect coupling strength between these resonators. Such coherent processes indicate that information encoded in vibrational modes can be transferred and stored between spatially separated resonators, which can open the venue of on-demand phonon-based information processing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1916978117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7084087PMC
March 2020

Author Correction: Strong indirect coupling between graphene-based mechanical resonators via a phonon cavity.

Nat Commun 2019 03 19;10(1):1343. Epub 2019 Mar 19.

CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, 230026, Anhui, China.

The original version of this Article contained a number of errors. As a result of this, changes have been made to both the PDF and the HTML versions of the Article. A full list of these changes is available online.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-019-09240-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6423086PMC
March 2019

Soft fibrin matrix downregulates DAB2IP to promote Nanog-dependent growth of colon tumor-repopulating cells.

Cell Death Dis 2019 02 15;10(3):151. Epub 2019 Feb 15.

Department of Gastroenterology, Zhongnan Hospital of Wuhan University, Wuhan, 430071, China.

Colon cancer stem cells (CSCs) have been shown to be responsible for the recurrence and metastasis of colorectal cancer (CRC). As a crucial microenvironmental factor, extracellular matrix (ECM) stiffness is known to affect the stemness of CSCs. Recently, fibrin deposition in the stroma of CRC was demonstrated to be responsible for tumor development. In this study, we used salmon fibrin gel to provide a 3D ECM for colon cancer cells and investigated its effects on cell growth as well as the underlying mechanisms. Compared with stiff 420 Pascal (Pa) and 1 050 Pa gels, 90 Pa soft fibrin gel was most efficient at isolating and enriching tumor colonies. The size and number of colony formation negatively correlated with gel stiffness. Specifically, these tumor colonies exhibited efficient tumorigenicity, upregulated stem cell markers, and had anti-chemotherapeutic properties and were thus named tumor-repopulating cells (TRCs). More importantly, the self-renewal molecule Nanog was sharply induced in 3D-cultured colon TRCs; further, Nanog siRNA significantly inhibited colony formation, suggesting the indispensable role of Nanog in TRC growth. A subsequent mechanistic study illustrated that Nanog expression could be modulated through fibrin gel stiffness-induced DAB2IP/PI3K/FOXA1 signaling in colon TRCs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41419-019-1309-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6377646PMC
February 2019

Semiconductor quantum computation.

Natl Sci Rev 2019 Jan 22;6(1):32-54. Epub 2018 Dec 22.

Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei 230026, China.

Semiconductors, a significant type of material in the information era, are becoming more and more powerful in the field of quantum information. In recent decades, semiconductor quantum computation was investigated thoroughly across the world and developed with a dramatically fast speed. The research varied from initialization, control and readout of qubits, to the architecture of fault-tolerant quantum computing. Here, we first introduce the basic ideas for quantum computing, and then discuss the developments of single- and two-qubit gate control in semiconductors. Up to now, the qubit initialization, control and readout can be realized with relatively high fidelity and a programmable two-qubit quantum processor has even been demonstrated. However, to further improve the qubit quality and scale it up, there are still some challenges to resolve such as the improvement of the readout method, material development and scalable designs. We discuss these issues and introduce the forefronts of progress. Finally, considering the positive trend of the research on semiconductor quantum devices and recent theoretical work on the applications of quantum computation, we anticipate that semiconductor quantum computation may develop fast and will have a huge impact on our lives in the near future.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/nsr/nwy153DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8291422PMC
January 2019

The effects of one-lung ventilation mode on lung function in elderly patients undergoing esophageal cancer surgery.

Medicine (Baltimore) 2018 Jan;97(1):e9500

Department of Anesthesia, Jining No. 1 People's Hospital, Jining City, Shandong Province, China.

The objective of the present study was to explore the effects of different one-lung ventilation (OLV) modes on lung function in elderly patients undergoing esophageal cancer surgery. A total of 180 consecutive elderly patients (ASA Grades I-II, with OLV indications) undergoing elective surgery were recruited in the study. Patients were randomly divided into 4 groups (n = 45). In Group A, patients received low tidal volume (VT < 8 mL/kg) + pressure controlled ventilation (PCV), low tidal volume (VT < 8 mL/kg) + volume-controlled ventilation (VCV) in Group B, high tidal volume (VT ≥ 8 mL/kg) + PCV in Group C and high tidal volume (VT ≥ 8 mL/kg) + VCV in Group D. Two-lung ventilation involved routine tidal volume (8-10 mL/kg) at a frequency of 12 to 18 times/min, and VCV mode. Clinical efficacy among 4 groups was compared. The partial pressure of end-tidal carbon dioxide (PetCO2) did not significantly differ among 4 groups (all P > .05), and the oxygenation index and SO2 in Group A were significantly higher than in the other groups (P < .05). The PetCO2, peak airway pressure (Ppeak), platform airway pressure (Pplat), and mean airway pressure (Pmean) in Group A were significantly lower than those in the other groups (all P < .05). However, airway resistance (Raw) among 4 groups did not significantly differ (all P > .05). The incidence of pulmonary infection, anastomotic fistula, ventilator-induced lung injury, lung dysfunction, difficulty weaning from mechanical ventilation, and multiple organ dysfunction in Groups A and B were lower than that in Groups C and D (all P < .05). The expression levels of IL-6, tumor necrosis factor-α, and C-reactive protein in lavage fluid in Group A were significantly lower than those in the other groups (all P < .05). OLV with low tidal volume (VT < 8 mL/kg) + PCV (5 cmH2O PEEP) improved lung function and mitigated inflammatory responses in elderly patients undergoing esophageal cancer surgery.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/MD.0000000000009500DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5943101PMC
January 2018

Coupling a Germanium Hut Wire Hole Quantum Dot to a Superconducting Microwave Resonator.

Nano Lett 2018 03 27;18(3):2091-2097. Epub 2018 Feb 27.

Key Laboratory of Quantum Information, CAS , University of Science and Technology of China , Hefei , Anhui 230026 , China.

Realizing a strong coupling between spin and resonator is an important issue for scalable quantum computation in semiconductor systems. Benefiting from the advantages of a strong spin-orbit coupling strength and long coherence time, the Ge hut wire, which is proposed to be site-controlled grown for scalability, is considered to be a promising candidate to achieve this goal. Here we present a hybrid architecture in which an on-chip superconducting microwave resonator is coupled to the holes in a Ge quantum dot. The charge stability diagram can be obtained from the amplitude and phase responses of the resonator independently from the DC transport measurement. Furthermore, we estimate the hole-resonator coupling rate of g/2π = 148 MHz in the single quantum dot-resonator system and estimate the spin-resonator coupling rate g/2π to be in the range 2-4 MHz. We anticipate that strong coupling between hole spins and microwave photons in a Ge hut wire is feasible with optimized schemes in the future.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.8b00272DOI Listing
March 2018

Strong indirect coupling between graphene-based mechanical resonators via a phonon cavity.

Nat Commun 2018 01 26;9(1):383. Epub 2018 Jan 26.

CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, 230026, Anhui, China.

Mechanical resonators are promising systems for storing and manipulating information. To transfer information between mechanical modes, either direct coupling or an interface between these modes is needed. In previous works, strong coupling between different modes in a single mechanical resonator and direct interaction between neighboring mechanical resonators have been demonstrated. However, coupling between distant mechanical resonators, which is a crucial request for long-distance classical and quantum information processing using mechanical devices, remains an experimental challenge. Here, we report the experimental observation of strong indirect coupling between separated mechanical resonators in a graphene-based electromechanical system. The coupling is mediated by a far-off-resonant phonon cavity through virtual excitations via a Raman-like process. By controlling the resonant frequency of the phonon cavity, the indirect coupling can be tuned in a wide range. Our results may lead to the development of gate-controlled all-mechanical devices and open up the possibility of long-distance quantum mechanical experiments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-018-02854-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5786116PMC
January 2018

Electrotunable artificial molecules based on van der Waals heterostructures.

Sci Adv 2017 10 20;3(10):e1701699. Epub 2017 Oct 20.

CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, Anhui 230026, China.

Quantum confinement has made it possible to detect and manipulate single-electron charge and spin states. The recent focus on two-dimensional (2D) materials has attracted significant interests on possible applications to quantum devices, including detecting and manipulating either single-electron charging behavior or spin and valley degrees of freedom. However, the most popular model systems, consisting of tunable double-quantum-dot molecules, are still extremely difficult to realize in these materials. We show that an artificial molecule can be reversibly formed in atomically thin MoS sandwiched in hexagonal boron nitride, with each artificial atom controlled separately by electrostatic gating. The extracted values for coupling energies at different regimes indicate a single-electron transport behavior, with the coupling strength between the quantum dots tuned monotonically. Moreover, in the low-density regime, we observe a decrease of the conductance with magnetic field, suggesting the observation of Coulomb blockade weak anti-localization. Our experiments demonstrate for the first time the realization of an artificial quantum-dot molecule in a gated MoS van der Waals heterostructure, which could be used to investigate spin-valley physics. The compatibility with large-scale production, gate controllability, electron-hole bipolarity, and new quantum degrees of freedom in the family of 2D materials opens new possibilities for quantum electronics and its applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/sciadv.1701699DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5650488PMC
October 2017

Coupling graphene nanomechanical motion to a single-electron transistor.

Nanoscale 2017 May;9(17):5608-5614

Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China.

Graphene-based electromechanical resonators have attracted great interest recently because of the outstanding mechanical and electrical properties of graphene and their various applications. However, the coupling between mechanical motion and charge transport has not been explored in graphene. Herein, we studied the mechanical properties of a suspended 50 nm wide graphene nanoribbon, which also acts as a single-electron transistor (SET) at low temperatures. Using the SET as a sensitive detector, we found that the resonance frequency could be tuned from 82 MHz to 100 MHz and the quality factor exceeded 30 000. The strong charge-mechanical coupling was demonstrated by observing the SET induced ∼140 kHz resonance frequency shifts and mechanical damping. We also found that the SET can enhance the nonlinearity of the resonator. Our SET-coupled graphene mechanical resonator could approach an ultra-sensitive mass resolution of ∼0.55 × 10 g and a force sensitivity of ∼1.9 × 10 N (Hz), and can be further improved. These properties indicate that our device is a good platform for both fundamental physical studies and potential applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c6nr09768eDOI Listing
May 2017

Coherent Phonon Rabi Oscillations with a High-Frequency Carbon Nanotube Phonon Cavity.

Nano Lett 2017 02 11;17(2):915-921. Epub 2017 Jan 11.

Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences , Hefei 230026, China.

Phonon-cavity electromechanics allows the manipulation of mechanical oscillations similar to photon-cavity systems. Many advances on this subject have been achieved in various materials. In addition, the coherent phonon transfer (phonon Rabi oscillations) between the phonon cavity mode and another oscillation mode has attracted many interest in nanoscience. Here, we demonstrate coherent phonon transfer in a carbon nanotube phonon-cavity system with two mechanical modes exhibiting strong dynamical coupling. The gate-tunable phonon oscillation modes are manipulated and detected by extending the red-detuned pump idea of photonic cavity electromechanics. The first- and second-order coherent phonon transfers are observed with Rabi frequencies 591 and 125 kHz, respectively. The frequency quality factor product fQ ∼ 2 × 10 Hz achieved here is larger than kT/h, which may enable the future realization of Rabi oscillations in the quantum regime.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.6b04223DOI Listing
February 2017

Improving the luminescence enhancement of hybrid Au nanoparticle-monolayer MoS2 by focusing radially-polarized beams.

Opt Express 2016 Nov;24(24):27554-27562

Monolayer transition-metal dichalcogenides (TMDs) have grown as fantastic building blocks for optoelectronic applications, owing to their direct band gap, transparency, and mechanical flexibility. Since the luminescence of monolayer TMDs suffers from low light absorption and emission, surface plasmons, which confine light at subwavelength and enhance the local electric field, are utilized to boost both excitation and emission fields of TMDs, enabling strong light-matter interaction at the nano-scale. Meanwhile, radially-polarized beams (RPBs) as new and attractive excitation source have found many applications in surface plasmon polaritons, optical tweezer and so on. Here, by using RPBs, we demonstrate the photoluminescence (PL) enhancement of monolayer molybdenum disulfide (MoS2) hybridized with 210 nm-diameter gold nanoparticle (AuNP) is improved by about 1.37-fold compared with linearly-polarized beams (LPBs). Besides, the PL enhancement with RPBs depends on the size of AuNP as well. With 210nm-diameter AuNP, the PL enhancement is more than 1.5-fold higher than that with 60nm-diameter AuNP. This study highlights that RPBs are superior to LPBs for tuning the near-field system response and shows that RPBs drive a valuable avenue to further study the emerging two-dimentional materials.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.24.027554DOI Listing
November 2016

Strongly Coupled Nanotube Electromechanical Resonators.

Nano Lett 2016 09 5;16(9):5456-62. Epub 2016 Aug 5.

Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences , Hefei 230026, China.

Coupling an electromechanical resonator with carbon-nanotube quantum dots is a significant method to control both the electronic charge and the spin quantum states. By exploiting a novel microtransfer technique, we fabricate two separate strongly coupled and electrically tunable mechanical resonators for the first time. The frequency of the two resonators can be individually tuned by the bottom gates, and in each resonator, the electron transport through the quantum dot can be strongly affected by the phonon mode and vice versa. Furthermore, the conductance of either resonator can be nonlocally modulated by the other resonator through phonon-phonon interaction between the two resonators. Strong coupling is observed between the phonon modes of the two resonators, where the coupling strength larger than 200 kHz can be reached. This strongly coupled nanotube electromechanical resonator array provides an experimental platform for future studies of the coherent electron-phonon interaction, the phonon-mediated long-distance electron interaction, and entanglement state generation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.6b01875DOI Listing
September 2016

Parametric strong mode-coupling in carbon nanotube mechanical resonators.

Nanoscale 2016 Aug 22;8(31):14809-13. Epub 2016 Jul 22.

Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China.

Carbon nanotubes (CNTs) have attracted much attention for use in nanomechanical devices because of their exceptional properties, such as large resonant frequencies, low mass, and high quality factors. Here, we report the first experimental realization of parametric strong coupling between two mechanical modes on a single CNT nanomechanical resonator, by applying an extra microwave pump. This parametric pump method can be used to couple mechanical modes with arbitrary frequency differences. The properties of the mechanical resonator are detected by single-electron tunneling at low temperature, which is found to be strongly coupled to both modes. The coupling strength between the two modes can be tuned by the pump power, setting the coupling regime from weak to strong. This tunability may be useful in further phonon manipulations in carbon nanotubes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c6nr02853eDOI Listing
August 2016

Tunable capacitive coupling between two semiconductor charge qubits.

Nanotechnology 2016 Aug 29;27(32):324003. Epub 2016 Jun 29.

Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China. Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.

Strong coupling between two qubits is one of the main requirements for high fidelity two-qubit logic operations. Here we experimentally investigate the capacitive coupling between two double quantum dots. A pair of open slot confinement gates is used to enhance the coupling. We find that the coupling energy J can be conveniently tuned in a broad range. Through numerical simulations, we study the effect of J on two-qubit operations. The analysis shows that our experimentally obtained J is adequate to achieve high fidelity two-qubit entanglement and logic gates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/0957-4484/27/32/324003DOI Listing
August 2016

Tunable Hybrid Qubit in a GaAs Double Quantum Dot.

Phys Rev Lett 2016 Feb 25;116(8):086801. Epub 2016 Feb 25.

Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China.

We experimentally demonstrate a tunable hybrid qubit in a five-electron GaAs double quantum dot. The qubit is encoded in the (1,4) charge regime of the double dot and can be manipulated completely electrically. More importantly, dot anharmonicity leads to quasiparallel energy levels and a new anticrossing, which help preserve quantum coherence of the qubit and yield a useful working point. We have performed Larmor precession and Ramsey fringe experiments near the new working point and find that the qubit decoherence time is significantly improved over a charge qubit. This work shows a new way to encode a semiconductor qubit that is controllable and coherent.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevLett.116.086801DOI Listing
February 2016

Temperature dependence of Coulomb oscillations in a few-layer two-dimensional WS2 quantum dot.

Sci Rep 2015 Nov 5;5:16113. Epub 2015 Nov 5.

Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China.

Standard semiconductor fabrication techniques are used to fabricate a quantum dot (QD) made of WS2, where Coulomb oscillations were found. The full-width-at-half-maximum of the Coulomb peaks increases linearly with temperature while the height of the peaks remains almost independent of temperature, which is consistent with standard semiconductor QD theory. Unlike graphene etched QDs, where Coulomb peaks belonging to the same QD can have different temperature dependences, these results indicate the absence of the disordered confining potential. This difference in the potential-forming mechanism between graphene etched QDs and WS2 QDs may be the reason for the larger potential fluctuation found in graphene QDs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/srep16113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4633606PMC
November 2015

Charge Number Dependence of the Dephasing Rates of a Graphene Double Quantum Dot in a Circuit QED Architecture.

Phys Rev Lett 2015 Sep 17;115(12):126804. Epub 2015 Sep 17.

Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China.

We use an on-chip superconducting resonator as a sensitive meter to probe the properties of graphene double quantum dots at microwave frequencies. Specifically, we investigate the charge dephasing rates in a circuit quantum electrodynamics architecture. The dephasing rates strongly depend on the number of charges in the dots, and the variation has a period of four charges, over an extended range of charge numbers. Although the exact mechanism of this fourfold periodicity in dephasing rates is an open problem, our observations hint at the fourfold degeneracy expected in graphene from its spin and valley degrees of freedom.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1103/PhysRevLett.115.126804DOI Listing
September 2015

A gate defined quantum dot on the two-dimensional transition metal dichalcogenide semiconductor WSe2.

Nanoscale 2015 Oct;7(40):16867-73

Key Laboratory of Quantum Information, CAS, University of Science and Technology of China, Hefei, Anhui 230026, China.

Two-dimensional layered materials, such as transition metal dichalcogenides (TMDCs), are promising materials for future electronics owing to their unique electronic properties. With the presence of a band gap, atomically thin gate defined quantum dots (QDs) can be achieved on TMDCs. Herein, standard semiconductor fabrication techniques are used to demonstrate quantum confined structures on WSe2 with tunnel barriers defined by electric fields, therefore eliminating the edge states induced by etching steps, which commonly appear in gapless graphene QDs. Over 40 consecutive Coulomb diamonds with a charging energy of approximately 2 meV were observed, showing the formation of a QD, which is consistent with the simulations. The size of the QD could be tuned over a factor of 2 by changing the voltages applied to the top gates. These results shed light on a way to obtain smaller quantum dots on TMDCs with the same top gate geometry compared to traditional GaAs/AlGaAs heterostructures with further research.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c5nr04961jDOI Listing
October 2015

Ultra-wideband surface plasmonic Y-splitter.

Opt Express 2015 Sep;23(18):23270-7

We present an ultra-wideband Y-splitter based on planar THz plasmonic metamaterials, which consists of a straight waveguide with composite H-shaped structure and two branch waveguides with H-shaped structure. The spoof surface plasmonic polaritons (SSPPs) supported by the straight waveguide occupy the similar dispersion relation and mode characteristic to the ones confined by the branch waveguides. Attributing to these features, the two branch waveguides can equally separate the SSPPs wave propagating along the straight plasmonic waveguide to form a 3dB power divider in an ultra-wideband frequency range. To verify the functionality and performance of the proposed Y-splitter, we scaled down the working frequency to microwave and implemented microwave experiments. The tested device performances have clearly validated the functionality of our designs. It is believed to be applicable for future plasmonic circuit in microwave and THz ranges.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.23.023270DOI Listing
September 2015

Coupling Two Distant Double Quantum Dots with a Microwave Resonator.

Nano Lett 2015 Oct 2;15(10):6620-5. Epub 2015 Sep 2.

Key Laboratory of Quantum Information, University of Science and Technology of China, Chinese Academy of Sciences , Hefei 230026, China.

We fabricated a hybrid device with two distant graphene double quantum dots (DQDs) and a microwave resonator. A nonlinear response is observed in the resonator reflection amplitude when the two DQDs are jointly tuned to the vicinity of the degeneracy points. This observation can be well fitted by the Tavis-Cummings (T-C) model which describes two two-level systems coupling with one photonic field. Furthermore, the correlation between the DC currents in the two DQDs is studied. A nonzero cross-current correlation is observed which has been theoretically predicted to be an important sign of nonlocal coupling between two distant systems. Our results explore T-C physics in electronic transport and also contribute to the study of nonlocal transport and future implementations of remote electronic entanglement.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.nanolett.5b02400DOI Listing
October 2015

Assessment of pancreatic adenocarcinoma: Use of low-dose whole pancreatic CT perfusion and individualized dual-energy CT scanning.

J Med Imaging Radiat Oncol 2015 Oct 29;59(5):590-8. Epub 2015 Jul 29.

Shandong Provincial Medical Imaging Research Institute, Shandong University, Jinan, China.

Introduction: The objective of this study was to investigate the value of low-dose whole pancreatic computed tomography (CT) perfusion integrated with individualized dual-energy CT (DECT) scanning in the diagnosis of pancreatic adenocarcinoma.

Methods: Twenty patients with pancreatic adenocarcinoma underwent pancreatic CT perfusion as well as individualized dual-phase DECT pancreatic scans. Perfusion characteristics of non-tumourous pancreatic parenchyma and pancreatic adenocarcinoma were analysed. Weighted-average 120 kVp images and the optimal monoenergetic images in dual phase were reconstructed and the contrast noise ratio (CNR) of pancreas-to-tumour were compared.

Results: There were significant difference on blood flow as well as blood volume between pancreatic adenocarcinoma and the non-tumourous pancreatic parenchyma (P < 0.05), whereas no difference on permeability (P > 0.05). CNRs of pancreas-to-tumour in individualized pancreatic phase were significantly higher than those in venous phase (P < 0.05), and CNRs of optimal monoenergetic images were higher than those on weighted-average 120 kVp images (P < 0.05) in both phase. Total effective radiation dose of CT examination was around 9.32-13.75 mSv.

Conclusions: Low-dose whole pancreatic CT perfusion can provide functional information, and the individualized pancreatic phase DECT scan is the optimal method for detecting pancreatic adenocarcinomas. The integration of the two techniques has great value in clinical application.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/1754-9485.12342DOI Listing
October 2015
-->