TY - JOUR
AB - The ability to control the direction of scattered light is crucial to provide flexibility and scalability for a wide range of on-chip applications, such as integrated photonics, quantum information processing, and nonlinear optics. Tunable directionality can be achieved by applying external magnetic fields that modify optical selection rules, by using nonlinear effects, or interactions with vibrations. However, these approaches are less suitable to control microwave photon propagation inside integrated superconducting quantum devices. Here, we demonstrate on-demand tunable directional scattering based on two periodically modulated transmon qubits coupled to a transmission line at a fixed distance. By changing the relative phase between the modulation tones, we realize unidirectional forward or backward photon scattering. Such an in-situ switchable mirror represents a versatile tool for intra- and inter-chip microwave photonic processors. In the future, a lattice of qubits can be used to realize topological circuits that exhibit strong nonreciprocity or chirality.
AU - Redchenko, Elena
AU - Poshakinskiy, Alexander V.
AU - Sett, Riya
AU - Zemlicka, Martin
AU - Poddubny, Alexander N.
AU - Fink, Johannes M
ID - 13117
JF - Nature Communications
TI - Tunable directional photon scattering from a pair of superconducting qubits
VL - 14
ER -
TY - GEN
AB - This dataset comprises all data shown in the figures of the submitted article "Tunable directional photon scattering from a pair of superconducting qubits" at arXiv:2205.03293. Additional raw data are available from the corresponding author on reasonable request.
AU - Redchenko, Elena
AU - Poshakinskiy, Alexander
AU - Sett, Riya
AU - Zemlicka, Martin
AU - Poddubny, Alexander
AU - Fink, Johannes M
ID - 13124
TI - Tunable directional photon scattering from a pair of superconducting qubits
ER -
TY - JOUR
AB - State-of-the-art transmon qubits rely on large capacitors, which systematically improve their coherence due to reduced surface-loss participation. However, this approach increases both the footprint and the parasitic cross-coupling and is ultimately limited by radiation losses—a potential roadblock for scaling up quantum processors to millions of qubits. In this work we present transmon qubits with sizes as low as 36 × 39 µm2 with 100-nm-wide vacuum-gap capacitors that are micromachined from commercial silicon-on-insulator wafers and shadow evaporated with aluminum. We achieve a vacuum participation ratio up to 99.6% in an in-plane design that is compatible with standard coplanar circuits. Qubit relaxationtime measurements for small gaps with high zero-point electric field variance of up to 22 V/m reveal a double exponential decay indicating comparably strong qubit interaction with long-lived two-level systems. The exceptionally high selectivity of up to 20 dB to the superconductor-vacuum interface allows us to precisely back out the sub-single-photon dielectric loss tangent of aluminum oxide previously exposed to ambient conditions. In terms of future scaling potential, we achieve a ratio of qubit quality factor to a footprint area equal to 20 µm−2, which is comparable with the highest T1 devices relying on larger geometries, a value that could improve substantially for lower surface-loss superconductors.
AU - Zemlicka, Martin
AU - Redchenko, Elena
AU - Peruzzo, Matilda
AU - Hassani, Farid
AU - Trioni, Andrea
AU - Barzanjeh, Shabir
AU - Fink, Johannes M
ID - 14517
IS - 4
JF - Physical Review Applied
TI - Compact vacuum-gap transmon qubits: Selective and sensitive probes for superconductor surface losses
VL - 20
ER -
TY - GEN
AB - This dataset comprises all data shown in the figures of the submitted article "Compact vacuum gap transmon qubits: Selective and sensitive probes for superconductor surface losses" at arxiv.org/abs/2206.14104. Additional raw data are available from the corresponding author on reasonable request.
AU - Zemlicka, Martin
AU - Redchenko, Elena
AU - Peruzzo, Matilda
AU - Hassani, Farid
AU - Trioni, Andrea
AU - Barzanjeh, Shabir
AU - Fink, Johannes M
ID - 14520
TI - Compact vacuum gap transmon qubits: Selective and sensitive probes for superconductor surface losses
ER -
TY - THES
AB - Recent substantial advances in the feld of superconducting circuits have shown its
potential as a leading platform for future quantum computing. In contrast to classical
computers based on bits that are represented by a single binary value, 0 or 1, quantum
bits (or qubits) can be in a superposition of both. Thus, quantum computers can store
and handle more information at the same time and a quantum advantage has already
been demonstrated for two types of computational tasks. Rapid progress in academic
and industry labs accelerates the development of superconducting processors which may
soon fnd applications in complex computations, chemical simulations, cryptography, and
optimization. Now that these machines are scaled up to tackle such problems the questions
of qubit interconnects and networks becomes very relevant. How to route signals on-chip
between diferent processor components? What is the most efcient way to entangle
qubits? And how to then send and process entangled signals between distant cryostats
hosting superconducting processors?
In this thesis, we are looking for solutions to these problems by studying the collective
behavior of superconducting qubit ensembles. We frst demonstrate on-demand tunable
directional scattering of microwave photons from a pair of qubits in a waveguide. Such a
device can route microwave photons on-chip with a high diode efciency. Then we focus
on studying ultra-strong coupling regimes between light (microwave photons) and matter
(superconducting qubits), a regime that could be promising for extremely fast multi-qubit
entanglement generation. Finally, we show coherent pulse storage and periodic revivals
in a fve qubit ensemble strongly coupled to a resonator. Such a reconfgurable storage
device could be used as part of a quantum repeater that is needed for longer-distance
quantum communication.
The achieved high degree of control over multi-qubit ensembles highlights not only the
beautiful physics of circuit quantum electrodynamics, it also represents the frst step
toward new quantum simulation and communication methods, and certain techniques
may also fnd applications in future superconducting quantum computing hardware.
AU - Redchenko, Elena
ID - 12366
SN - 2663-337X
TI - Controllable states of superconducting Qubit ensembles
ER -
TY - GEN
AB - This dataset comprises all data shown in the figures of the submitted article "Geometric superinductance qubits: Controlling phase delocalization across a single Josephson junction". Additional raw data are available from the corresponding author on reasonable request.
AU - Peruzzo, Matilda
AU - Hassani, Farid
AU - Szep, Grisha
AU - Trioni, Andrea
AU - Redchenko, Elena
AU - Zemlicka, Martin
AU - Fink, Johannes M
ID - 13057
TI - Geometric superinductance qubits: Controlling phase delocalization across a single Josephson junction
ER -
TY - JOUR
AB - There are two elementary superconducting qubit types that derive directly from the quantum harmonic oscillator. In one, the inductor is replaced by a nonlinear Josephson junction to realize the widely used charge qubits with a compact phase variable and a discrete charge wave function. In the other, the junction is added in parallel, which gives rise to an extended phase variable, continuous wave functions, and a rich energy-level structure due to the loop topology. While the corresponding rf superconducting quantum interference device Hamiltonian was introduced as a quadratic quasi-one-dimensional potential approximation to describe the fluxonium qubit implemented with long Josephson-junction arrays, in this work we implement it directly using a linear superinductor formed by a single uninterrupted aluminum wire. We present a large variety of qubits, all stemming from the same circuit but with drastically different characteristic energy scales. This includes flux and fluxonium qubits but also the recently introduced quasicharge qubit with strongly enhanced zero-point phase fluctuations and a heavily suppressed flux dispersion. The use of a geometric inductor results in high reproducibility of the inductive energy as guaranteed by top-down lithography—a key ingredient for intrinsically protected superconducting qubits.
AU - Peruzzo, Matilda
AU - Hassani, Farid
AU - Szep, Gregory
AU - Trioni, Andrea
AU - Redchenko, Elena
AU - Zemlicka, Martin
AU - Fink, Johannes M
ID - 9928
IS - 4
JF - PRX Quantum
KW - quantum physics
KW - mesoscale and nanoscale physics
TI - Geometric superinductance qubits: Controlling phase delocalization across a single Josephson junction
VL - 2
ER -
TY - JOUR
AB - Practical quantum networks require low-loss and noise-resilient optical interconnects as well as non-Gaussian resources for entanglement distillation and distributed quantum computation. The latter could be provided by superconducting circuits but existing solutions to interface the microwave and optical domains lack either scalability or efficiency, and in most cases the conversion noise is not known. In this work we utilize the unique opportunities of silicon photonics, cavity optomechanics and superconducting circuits to demonstrate a fully integrated, coherent transducer interfacing the microwave X and the telecom S bands with a total (internal) bidirectional transduction efficiency of 1.2% (135%) at millikelvin temperatures. The coupling relies solely on the radiation pressure interaction mediated by the femtometer-scale motion of two silicon nanobeams reaching a Vπ as low as 16 μV for sub-nanowatt pump powers. Without the associated optomechanical gain, we achieve a total (internal) pure conversion efficiency of up to 0.019% (1.6%), relevant for future noise-free operation on this qubit-compatible platform.
AU - Arnold, Georg M
AU - Wulf, Matthias
AU - Barzanjeh, Shabir
AU - Redchenko, Elena
AU - Rueda Sanchez, Alfredo R
AU - Hease, William J
AU - Hassani, Farid
AU - Fink, Johannes M
ID - 8529
JF - Nature Communications
KW - General Biochemistry
KW - Genetics and Molecular Biology
KW - General Physics and Astronomy
KW - General Chemistry
SN - 2041-1723
TI - Converting microwave and telecom photons with a silicon photonic nanomechanical interface
VL - 11
ER -
TY - GEN
AB - This datasets comprises all data shown in plots of the submitted article "Converting microwave and telecom photons with a silicon photonic nanomechanical interface". Additional raw data are available from the corresponding author on reasonable request.
AU - Arnold, Georg M
AU - Wulf, Matthias
AU - Barzanjeh, Shabir
AU - Redchenko, Elena
AU - Rueda Sanchez, Alfredo R
AU - Hease, William J
AU - Hassani, Farid
AU - Fink, Johannes M
ID - 13056
TI - Converting microwave and telecom photons with a silicon photonic nanomechanical interface
ER -
TY - JOUR
AB - Mechanical systems facilitate the development of a hybrid quantum technology comprising electrical, optical, atomic and acoustic degrees of freedom1, and entanglement is essential to realize quantum-enabled devices. Continuous-variable entangled fields—known as Einstein–Podolsky–Rosen (EPR) states—are spatially separated two-mode squeezed states that can be used for quantum teleportation and quantum communication2. In the optical domain, EPR states are typically generated using nondegenerate optical amplifiers3, and at microwave frequencies Josephson circuits can serve as a nonlinear medium4,5,6. An outstanding goal is to deterministically generate and distribute entangled states with a mechanical oscillator, which requires a carefully arranged balance between excitation, cooling and dissipation in an ultralow noise environment. Here we observe stationary emission of path-entangled microwave radiation from a parametrically driven 30-micrometre-long silicon nanostring oscillator, squeezing the joint field operators of two thermal modes by 3.40 decibels below the vacuum level. The motion of this micromechanical system correlates up to 50 photons per second per hertz, giving rise to a quantum discord that is robust with respect to microwave noise7. Such generalized quantum correlations of separable states are important for quantum-enhanced detection8 and provide direct evidence of the non-classical nature of the mechanical oscillator without directly measuring its state9. This noninvasive measurement scheme allows to infer information about otherwise inaccessible objects, with potential implications for sensing, open-system dynamics and fundamental tests of quantum gravity. In the future, similar on-chip devices could be used to entangle subsystems on very different energy scales, such as microwave and optical photons.
AU - Barzanjeh, Shabir
AU - Redchenko, Elena
AU - Peruzzo, Matilda
AU - Wulf, Matthias
AU - Lewis, Dylan
AU - Arnold, Georg M
AU - Fink, Johannes M
ID - 6609
JF - Nature
TI - Stationary entangled radiation from micromechanical motion
VL - 570
ER -
TY - JOUR
AB - Spontaneous emission spectra of two initially excited closely spaced identical atoms are very sensitive to the strength and the direction of the applied magnetic field. We consider the relevant schemes that ensure the determination of the mutual spatial orientation of the atoms and the distance between them by entirely optical means. A corresponding theoretical description is given accounting for the dipole-dipole interaction between the two atoms in the presence of a magnetic field and for polarizations of the quantum field interacting with magnetic sublevels of the two-atom system.
AU - Redchenko, Elena
AU - Makarov, Alexander
AU - Yudson, Vladimir
ID - 307
IS - 4
JF - Physical Review A - Atomic, Molecular, and Optical Physics
TI - Nanoscopy of pairs of atoms by fluorescence in a magnetic field
VL - 97
ER -
TY - JOUR
AB - We study a polar molecule immersed in a superfluid environment, such as a helium nanodroplet or a Bose–Einstein condensate, in the presence of a strong electrostatic field. We show that coupling of the molecular pendular motion, induced by the field, to the fluctuating bath leads to formation of pendulons—spherical harmonic librators dressed by a field of many-particle excitations. We study the behavior of the pendulon in a broad range of molecule–bath and molecule–field interaction strengths, and reveal that its spectrum features a series of instabilities which are absent in the field-free case of the angulon quasiparticle. Furthermore, we show that an external field allows to fine-tune the positions of these instabilities in the molecular rotational spectrum. This opens the door to detailed experimental studies of redistribution of orbital angular momentum in many-particle systems. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
AU - Redchenko, Elena
AU - Lemeshko, Mikhail
ID - 1206
IS - 22
JF - ChemPhysChem
TI - Libration of strongly oriented polar molecules inside a superfluid
VL - 17
ER -