Jaw-Shen Tsai's research while affiliated with Tokyo University of Science and other places
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Publications (62)
In quantum information processing, two primary research directions have emerged: one based on discrete variables (DV) and the other on the structure of quantum states in a continuous-variable (CV) space. It is increasingly recognized that integrating these two approaches could unlock new potentials, overcoming the inherent limitations of each. Here...
We develop a compact four-port superconducting switch with tunable operating frequency in the range from 4.8 to 7.3 GHz. Isolation between channels exceeds 20 dB over a bandwidth of several hundred megahertz, exceeding 40 dB at some frequencies. The footprint of the device is 80×420μm2. The tunability requires only a global flux bias without either...
Quantum tunneling is the phenomenon that makes superconducting circuits “quantum”. Recently, there has been a renewed interest in using quantum tunneling in phase space of a Kerr parametric oscillator as a resource for quantum information processing. Here, we report a direct observation of quantum interference induced by such tunneling and its dyna...
The initialization of superconducting qubits is one of the essential techniques for the realization of quantum computation. In previous research, initialization above 99% fidelity has been achieved at 280 ns. Here, we demonstrate the rapid initialization of a superconducting qubit with a quantum circuit refrigerator (QCR). Photon-assisted tunneling...
We experimentally investigate a superconducting circuit composed of two flux qubits ultrastrongly coupled to a common $LC$ resonator. Owing to the large anharmonicity of the flux qubits, the system can be correctly described by a generalized Dicke Hamiltonian containing spin-spin interaction terms. In the experimentally measured spectrum, an avoide...
Quantum tunneling is the phenomenon that makes superconducting circuits "quantum". Recently, there has been a renewed interest in using quantum tunneling in phase space of a Kerr parametric oscillator as a resource for quantum information processing. Here, we report a direct observation of quantum interference induced by such tunneling in a planar...
The initialization of superconducting qubits is one of the essential techniques for the realization of quantum computation. In previous research, initialization above 99\% fidelity has been achieved at 280 ns. Here, we demonstrate the rapid initialization of a superconducting qubit with a quantum-circuit refrigerator (QCR). Photon-assisted tunnelin...
We address the scaling-up problem for superconducting quantum circuits by using lumped-element resonators based on an alternative fabrication method of aluminum-aluminum oxide-aluminum (Al-AlOx-Al) parallel-plate capacitors. The size of the resonators is only 0.04mm2, which is more than one order smaller than the typical size of coplanar resonators...
![Figure 3. Experimental results by various groups [22-24] on the doping...](publication/369810131/figure/fig3/AS:11431281138429841@1680749323669/Experimental-results-by-various-groups-22-24-on-the-doping-dependence-of-the_Q320.jpg)
First-principles calculations for underdoped La2−xSrxCuO4 (LSCO) have revealed a Fermi surface consisting of spin-triplet (KS) particles at the antinodal Fermi-pockets and spin-singlet (SS) particles at the nodal Fermi-arcs in the presence of AF local order. By performing a unique method of calculating the electronic-spin state of overdoped LSCO an...
When a magnetic moment is embedded in a metal, it captures nearby itinerant electrons to form a so-called Kondo cloud. When magnetic impurities are sufficiently dense that their individual clouds overlap with each other they are expected to form a correlated electronic ground state. This is known as Kondo condensation and can be considered a magnet...
Injection locking is a well-established technique widely used in optics as well as solid-state devices for efficient suppression of noise. We present the spectroscopic characterization of the effect of the injection-locking signal (ILS) in mitigating the phase noise of a Josephson parametric oscillator, whose output oscillating phase undergoes inde...
We perform noise spectroscopy of a Josephson parametric oscillator (JPO) by implementing a microwave homodyne interferometric measurement scheme. We observe the fluctuations in the self-oscillating output field of the JPO for a long 10-s time interval in a single-shot measurement and characterize the phase and amplitude noise. Furthermore, we inves...
Injection locking is a well-established technique widely used in optics as well as solid-state devices for efficient suppression of noise. We present the spectroscopic characterization of the effect of the injection-locking signal (ILS) in mitigating the phase noise of a Josephson parametric oscillator (JPO), whose output oscillating phase undergoe...
We perform the noise spectroscopy of a Josephson parametric oscillator (JPO) by implementing a microwave homodyne interferometric measurement scheme. We observe the fluctuations in the self-oscillating output field of the JPO for a long 10 s time interval in a single shot measurement and characterize the phase and amplitude noise. Furthermore, we i...
One-way quantum computing is a promising candidate for fault-tolerant quantum computing. Here, we propose protocols to realize a deterministic one-way controlled-not (cnot) gate and one-way X rotations on current quantum-computing platforms. By applying a delayed-choice scheme, we overcome a limit of most currently available quantum computers, whic...
Autonomous quantum error correction has gained considerable attention to avoid complicated measurements and feedback. Despite its simplicity compared with the conventional measurement-based quantum error correction, it is still a far from practical technique because of significant hardware overhead. We propose an autonomous quantum error correction...
We address the scaling-up problem for superconducting quantum circuits by using lumped-element resonators based on a new fabrication method of aluminum -- aluminum oxide -- aluminum ($\mathrm{Al/AlO_x/Al}$) parallel-plate capacitors. The size of the resonators is only 0.04$~\mathrm{mm^2}$, which is more than one order smaller than the typical size...
Autonomous quantum error correction has gained considerable attention to avoid complicated measurements and feedback. Despite its simplicity compared with the conventional measurement-based quantum error correction, it is still a far from practical technique because of significant hardware overhead. We propose an autonomous quantum error correction...
One-way quantum computing is a promising candidate for fault-tolerant quantum computing. Here, we propose new protocols to realize a deterministic one-way CNOT gate and one-way $X$-rotations on quantum-computing platforms. By applying a delayed-choice scheme, we overcome a limit of most currently available quantum computers, which are unable to imp...
We propose a design to realize integrated broadband nonreciprocal microwave isolators and circulators using superconducting circuit elements without any magnetic materials. To obtain a broadband response, we develop a waveguide-based design by temporal modulations. The corresponding compact traveling-wave structure is implemented with integrated su...
We propose a design to realize integrated broadband nonreciprocal microwave isolators and circulators using superconducting circuit elements without any magnetic materials. To obtain a broadband response, we develop a waveguide-based design by temporal modulations. The corresponding compact traveling-wave structure is implemented with integrated su...
We report an experimentally observed anomalous doubly split spectrum and its split-width fluctuation in an ultrastrongly coupled superconducting qubit and resonator. From an analysis of Rabimodel and circuit model Hamiltonians, we found that the doubly split spectrum and split-width fluctuation are caused by discrete charge hops due to quasiparticl...
Cluster states, a type of highly entangled state, are essential resources for quantum information processing. Here we demonstrated the generation of a time-domain linear cluster state (t-LCS) using a superconducting quantum circuit consisting of only two transmon qubits. By recycling the physical qubits, the t-LCS equivalent up to four physical qub...
In this Tutorial, we introduce basic conceptual elements to understand and build a gate-based superconducting quantum computing system.
In 1986 Bednorz and Műller discovered high temperature superconductivity in copper oxides by chemically doping holes into La2CuO4 (LCO), the antiferromagnetic insulator. Despite intense experimental and theoretical research during the past 34 years, no general consensus on the electronic-spin structures and the origin of pseudogap has been obtained...
In this tutorial, we introduce basic conceptual elements to understand and build a gate-based superconducting quantum computing system.
Among the major hardware platforms for large-scale quantum computing, one of the leading candidates is superconducting quantum circuits. Current proposed architectures for quantum error-correction with the promising surface code require a two-dimensional layout of superconducting qubits with nearest-neighbor interactions. A major hurdle for the sca...
We propose a novel architecture for superconducting circuits to improve the efficiency of a quantum annealing system. To increase the capability of a circuit, it is desirable for a qubit to be coupled not only with adjacent qubits but also with other qubits located far away. We introduce a circuit that uses a lumped element resonator coupled each w...
Research towards the realization of superconducting quantum computers is progressing rapidly. Recently, the number of integrated quantum bits (qubits) has begun to exceed 50 bits, and such quantum system has the potential capability to surpass that of any classical computer (quantum supremacy). To improve gate fidelity, research on qubits and surro...
This paper is dedicated to Professor K. Alex Müller. In 1986, 30 years ago, high temperature superconductivity was discovered by George Bednorz and Alex Müller in copper oxides, by their epoch-making insight that higher superconducting transition temperature could be achieved by strong interactions with Jahn-Teller (JT) distortion of the constituti...
The magnetic field is shown to affect significantly non-equilibrium quasiparticle (QP) distributions under conditions of inverse proximity effect on the remarkable example of a single-electron hybrid turnstile. This effect suppresses the gap in the superconducting leads in the vicinity of turnstile junctions with a Coulomb blockaded island, thus, t...
In this paper, we clarified the origins of the pseudogap and the mechanism of d-wave superconductivity in copper oxide (cuparate) superconductors. Paying attention to the unusual property of cuparates, i.e. a deformation in the opposite direction to the Jahn-Teller distortion by doping holes, called the anti-Jahn-Teller effect, we show theoreticall...
Supplementary Figures 1-5, Supplementary Notes 1-5 and Supplementary References.
Single-photon detection is a requisite technique in quantum-optics experiments in both the optical and the microwave domains. However, the energy of microwave quanta are four to five orders of magnitude less than their optical counterpart, making the efficient detection of single microwave photons extremely challenging. Here we demonstrate the dete...
Single photon detection is a requisite technique in quantum-optics
experiments in both the optical and the microwave domains. However, the energy
of microwave quanta are four to five orders of magnitude less than their
optical counterpart, making the efficient detection of single microwave photons
extremely challenging. Here, we demonstrate the det...
Research is currently being conducted on quantum information processing, which is expected to be the next-generation approach to information processing. The development of quantum computers using superconducting circuits is an area of particularly intensive research and notable progress has been made. Achievements and outlook of this technology are...
As a step toward realizing the quantum current standard, single-electron pumping of parallel SINIS turnstiles was performed. Eleven SINIS turnstiles were fabricated on the same chip, and the number of operating SINIS turnstiles was increased one by one. As a result, 11 turnstiles were operated simultaneously up to 100 MHz, resulting in a pumped dc...
Single electron pumping by a SINIS turnstile is investigated up to 1 GHz in various conditions to realize a quantum current standard. A standard deviation of the pumping current at 100 MHz is about 10-4 at base temperature of a dilution refrigerator. As expected, the plateau of the pumped current degrades as temperature increases because of the the...
We infer the high-frequency flux noise spectrum in a superconducting flux
qubit by studying the decay of Rabi oscillations under strong driving
conditions. The large anharmonicity of the qubit and its strong inductive
coupling to a microwave line enabled high-amplitude driving without causing
significant additional decoherence. Rabi frequencies up...
In quantum information processing, knowledge of the noise in the system is
crucial for high-precision manipulation and tomography of coherent quantum
operations. Existing strategies for identifying this noise require the use of
additional quantum devices or control pulses. We present a noise-identification
method directly based on the system's non-...
We study dispersive readout in superconducting flux qubits which are
capacitively coupled to a superconducting cavity with ˜ 10 GHz
resonant frequency fr. To discriminate the state of the qubit
precisely, large magnitude of the dispersive shift χ is desirable.
For the two-level system, χ is given by g^2/δ where g is the
coupling strength and δ is t...
We report a direct measurement of the low-frequency noise spectrum in a superconducting flux qubit. Our method uses the noise sensitivity of a free-induction Ramsey interference experiment, comprising free evolution in the presence of noise for a fixed period of time followed by single-shot qubit-state measurement. Repeating this procedure enables...
We report a direct measurement of the transverse and longitudinal low-frequency noise that causes dephasing of superconducting flux qubits. The former is due to flux fluctuations, and it affects the qubit's energy detuning; the latter is parameterized as effective critical-current or charge fluctuations, and affects the tunnel coupling between the...
Quantum coherence in natural and artificial spin systems is fundamental to applications ranging from quantum information science to magnetic-resonance imaging and identification. Several multipulse control sequences targeting generalized noise models have been developed to extend coherence by dynamically decoupling a spin system from its noisy envi...
Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as wel...
We present measurements on a superconducting flux qubit where the tunnel coupling Delta can be varied from 0.8 to 4.8 GHz. This allows for both ZZ and XZ qubit-qubit coupling architectures. The device is realized by replacing one of the Josephson junctions in the qubit with an additional loop which forms a dc SQUID. By applying different fluxes in...
We report relaxation times T1 in excess of 10 mus in aluminum persistent-current qubits (flux qubits), read out by a switching dc SQUID. At the sweet spot in flux bias, spin-echo refocusing gives a relaxation-limited coherence time T2=2T1. The free-induction decay time constant T2^* reaches 2.5 mus. Detuning the quantization axis away from this opt...
We have fabricated an Al based single-electron transistor transistor (SET) whose island is suspended above the substrate. The structure can be considered as a two-in-one device containing a doubly clamped beam and a transducer that converts mechanical vibrations into variations in the SET current. In addition to the regular side gate, a bottom gate...
Intensive research on the construction of superconducting quantum computers has produced numerous important achievements. The quantum bit (qubit), based on the Josephson junction, is at the heart of this research. This macroscopic system has the ability to control quantum coherence. This article reviews the current state of quantum computing as wel...
We have studied nonlinear superconducting resonators: lambda/2 coplanar-waveguide (CPW) resonators with Josephson junctions (JJs) placed in the middle and lambda/4 CPW resonators terminated by JJs, which can be used for the qubit readout as "bifurcation amplifiers." The nonlinearity of the resonators arises from the Josephson junctions, and because...
The authors have studied Nb λ/2 coplanar-waveguide (CPW) resonators whose resonant frequencies are 10–11 GHz. The resonators have different film thicknesses, t=0.05 , 0.1, 0.2, and 0.3 μ m . They measured at low temperatures, T=0.02–5 K , one of the scattering-matrix element, S<sub>21</sub> , which is the transmission coefficient from one port to t...
We have studied low-temperature electrical transport properties of nanoscale Nb/(Al–)Al2O3/Nb and NbN/AlN/NbN Josephson junctions (JJs) fabricated by focused-ion-beam (FIB) milling. This FIB fabrication process yields high-quality JJs whose superconducting gap energy agrees with the bulk value. In this paper, we report the improvement in the precis...
When the quantum oscillations [Pashkin et al., Nature 421, 823 (2003)] and the conditional gate operation [Yamamoto et al., Nature 425, 941 (2003)] were demonstrated using superconducting charge qubits, the charge qubits were coupled capacitively, where the coupling was always on and the coupling strength was not tunable. This fixed coupling, howev...
We discuss a practical design for tunably coupling a pair of flux qubits via the quantum inductance of a third high-frequency qubit. The design is particularly well suited for realizing a recently proposed microwave-induced parametric coupling scheme. This is attractive because the qubits can always remain at their optimal points. Furthermore, we w...
The technologies of Josephson-junction-based qubits have been progressing rapidly, ever since its first demonstration by a superconducting charge qubit1. A variety of systems have been implemented with remarkable progress in coherence time and read-out schemes. Although the current level of this solid-state device is still not as advanced as that o...
We have developed a fabrication process for nanoscale tunnel junctions which includes focused-ion-beam etching from different directions. By applying the process to a Nb/(Al-)Al_2O_3/Nb trilayer, we have fabricated a Nb single-electron transistor (SET), and characterized the SET at low temperatures, T=0.04-40 K. The superconducting gap energy and t...
We have measured resistively coupled single electron transistors under two bias conditions: asymmetric
and symmetric. We observed a characteristic Coulomb blockade pattern whose shape is significantly
different for the two cases. Our simulations based on the orthodox theory of single-electron tunneling are in
good qualitative agreement with the...
We have fabricated and measured a resistively coupled single electron transistor (R-SET). In our implementation, a chromium thin-film resistive gate was connected directly to a mesoscopic island formed between two ultrasmall Al/AlOx/Al tunnel junctions. The transistor was fabricated by electron beam lithography using the suspended bridge technique....
Citations
... In our previous work [29], we experimentally demonstrated that such conversion in a superconducting KPO preserves the quantum coherence of the system, with the underlying physics being quantum tunnelling in phase space [30,31]. Furthermore, we ...
... This device, called quantum circuit refrigerator (QCR), can operate as a tunable source of dissipation for quantum-electric devices such as qubits [44][45][46][47]. More recently, the qubit reset with QCR was demonstrated [48,49]. While several works on the effect of the QCR on linear resonators, two-level systems and transmons have been reported, it remains largely unexplored for periodically-driven systems such as KPOs. ...
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... However, recently there has been an increasing interest in finding ways to miniaturize them. One way is to use lumped-element resonators 77 , the lateral size of which is already less than 200 microns at a frequency of 7 GHz and this is not the limit. Moreover, desired increase in the reading frequency will also lead to a further reduction in the size of the resonators. ...
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... The discovery of Kondo condensation [22] in silicon metals with high levels of impurity constitutes a significant advancement in elucidating the intricate principles governing electronelectron interactions, disorder, and spin correlations in solid materials. In metals, introducing a magnetic moment captures nearby free electrons, forming a 'Kondo cloud' that may span several micrometers. ...
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... [56][57][58][59][60] This Special Issue offers broad coverage of noise studies pertinent to the development of quantum device technologies, including noise in the semiconductor quantum dots, Josephson junctions, parametric oscillators, Bi 2 Se 3 topological thin films, entangled electron systems, microwave resonators, spin Hall nano-oscillators, superconducting aluminum devices, neuromorphic computing, and silicon spinqubits. [61][62][63][64][65][66][67][68][69][70][71] The theory developments, covered in this Special Issue, include simulation of noise in the ground state energy of electrons in gated quantum dots, theory of full counting statistics of ultrafast quantum transport, key exchanger, noise of topological insulators, thermal fluctuations in magnetic nanoparticle systems, non-Gaussian noise, second spectrum of fluctuations in graphene, noise-dissipation relation for nonlinear electronic circuits, and approaches for squeezing electronic noise. [72][73][74][75][76][77][78][79][80] In conclusion, this Special Issue presents an exciting selection of new experimental and theoretical results associated with electronic noise, including noise in advanced materials, electronic and optoelectronic devices, and quantum technologies. ...
... [29][30][31][32] A recent study on the noise characteristics of a Josephson parametric oscillator (JPO) shows the increase in the phase noise due to the random switching of the oscillator output phase between the two coexisting bistable states. 33 In this letter, we present the experimental investigation of the effect of a weak injection-locking signal (ILS) on resonance with the cavity frequency x s in the mitigation of the phase noise of a JPO operating above the threshold. A number of experiments and theoretical studies have demonstrated injection locking in solid-state systems, e.g., Josephson parametric phase-locked oscillators, 15,28,34,35 Josephson photonic devices, 36 masers, 37 lasers, 38 etc. ...
... Combining Hamiltonian engineering with dissipation engineering may enable us to create highly coherent cat states [66][67][68][69]. Finally, employing other multiphoton pumps may open new possibilities [70][71][72][73][74][75][76][77][78][79][80][81][82], such as exploring condensed matter physics in time crystals [83][84][85] and autonomous quantum error correction [86]. ...
... As listed in Table 6 and Table 7, superconducting is the most preferred by developers as an architecture of a quantum computing system. This is due to its advantages which are, high designability, scalability, easy to couple and easy to control [60,108]. ...
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... Our scheme eliminates the need for optical nonlinearity and strong static magnetic fields, which makes it suitably implemented with superconducting circuits. [69][70][71][72][73][74][75] This work may find potential applications in chiral quantum networks. ...
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... Fortunately, the related studies indicate that a class of CPW resonators with tunable Q L can be fulfilled by using an inductance transformer and DC-SQUID as the input-output coupling inductance of a CPW resonator [13][14][15]. This method used a magnetic field to tune the equivalent input-output coupling inductance of the CPW resonator. ...
