### 3482 results for qubit oscillator frequency

Contributors: Fedorov, Kirill

Date: 2013-01-01

This thesis presents experimental studies on developing of a novel fluxon readout for superconducting flux **qubits**. It is based on a scheme for detecting the microwave radiation of an **oscillating** fluxon in an annular Josephson junction (AJJ). The readout was implemented for a superconducting flux **qubit** coupled as a current dipole to the AJJ. An energy spectrum of the flux **qubit** was measured via detecting a **frequency** shift of the fluxon **oscillations** versus a flux bias through the **qubit**....**qubits** ... This thesis presents experimental studies on developing of a novel fluxon readout for superconducting flux **qubits**. It is based on a scheme for detecting the microwave radiation of an **oscillating** fluxon in an annular Josephson junction (AJJ). The readout was implemented for a superconducting flux **qubit** coupled as a current dipole to the AJJ. An energy spectrum of the flux **qubit** was measured via detecting a **frequency** shift of the fluxon **oscillations** versus a flux bias through the **qubit**.

Data types:

Contributors: Eugene Grichuk, Margarita Kuzmina, Eduard Manykin

Date: 2010-09-26

A network of coupled stochastic **oscillators** is
proposed for modeling of a cluster of entangled **qubits** that is
exploited as a computation resource in one-way quantum
computation schemes. A **qubit** model has been designed as a
stochastic **oscillator** formed by a pair of coupled limit cycle
**oscillators** with chaotically modulated limit cycle radii and
**frequencies**. The **qubit** simulates the behavior of electric field of
polarized light beam and adequately imitates the states of two-level
quantum system. A cluster of entangled **qubits** can be associated
with a beam of polarized light, light polarization degree being
directly related to cluster entanglement degree. Oscillatory network,
imitating **qubit** cluster, is designed, and system of equations for
network dynamics has been written. The constructions of one-**qubit**
gates are suggested. Changing of cluster entanglement degree caused
by measurements can be exactly calculated....network of stochastic **oscillators** ... A network of coupled stochastic **oscillators** is
proposed for modeling of a cluster of entangled **qubits** that is
exploited as a computation resource in one-way quantum
computation schemes. A **qubit** model has been designed as a
stochastic **oscillator** formed by a pair of coupled limit cycle
**oscillators** with chaotically modulated limit cycle radii and
**frequencies**. The **qubit** simulates the behavior of electric field of
polarized light beam and adequately imitates the states of two-level
quantum system. A cluster of entangled **qubits** can be associated
with a beam of polarized light, light polarization degree being
directly related to cluster entanglement degree. Oscillatory network,
imitating **qubit** cluster, is designed, and system of equations for
network dynamics has been written. The constructions of one-**qubit**
gates are suggested. Changing of cluster entanglement degree caused
by measurements can be exactly calculated.

Data types:

Top results from Data Repository sources. Show only results like these.

Contributors: Ying-Jie Chen, Hai-Tao Song, Jing-Lin Xiao

Date: 2017-10-14

Temperature effects on polaron in triangular quantum dot **qubit** subjected to an electromagnetic field are studied.
We derive the numerical results and formulate the derivative relationships of the ground and first
excited state energies, the electron probability density and the electron **oscillating** period in the superposition state of
the ground state and the first-excited state with the temperature, the cyclotron **frequency**, the electron-phonon coupling
constant, the electric field strength, the confinement strength and the Coulomb impurity potential, respectively....6-The electron **oscillating** period as functions of the temperature and the cyclotron **frequency** in triangular quantum dot **qubit** under an electric field.docx...7-The electron **oscillating** period as functions of the temperature and the electron-phonon coupling constant and etc. in triangular quantum dot **qubit** under an electric field.docx...2-The first excited state energy as functions of the temperature and the cyclotron **frequency** in triangular quantum dot **qubit** under an electric field.docx...3-The ground state energy as functions of the temperature and the electron-phonon coupling constant and etc. in triangular quantum dot **qubit** under an electric field.docx...1-The ground state energy as functions of the temperature and the cyclotron **frequency** in triangular quantum dot **qubit** under an electric field.docx ... Temperature effects on polaron in triangular quantum dot **qubit** subjected to an electromagnetic field are studied.
We derive the numerical results and formulate the derivative relationships of the ground and first
excited state energies, the electron probability density and the electron **oscillating** period in the superposition state of
the ground state and the first-excited state with the temperature, the cyclotron **frequency**, the electron-phonon coupling
constant, the electric field strength, the confinement strength and the Coulomb impurity potential, respectively.

Data types:

Contributors: Suter, Dieter, Klieber, Robert, Rippe, Lars, Nilsson, Mattias, Kröll, Stefan

Date: 2005-01-01

In optically controlled quantum computers it may be favorable to address different **qubits** using light with different **frequencies**, since the optical diffraction does not then limit the distance between **qubits**. Using **qubits** that are close to each other enables **qubit**-**qubit** interactions and gate operations that are strong and fast in comparison to **qubit**-environment interactions and decoherence rates. However, as **qubits** are addressed in **frequency** space, great care has to be taken when designing the laser pulses, so that they perform the desired operation on one **qubit**, without affecting other **qubits**. Complex hyperbolic secant pulses have theoretically been shown to be excellent for such **frequency**-addressed quantum computing [I. Roos and K. Molmer, Phys. Rev. A 69, 022321 (2004)]—e.g., for use in quantum computers based on optical interactions in rare-earth-metal-ion-doped crystals. The optical transition lines of the rare-earth-metal-ions are inhomogeneously broadened and therefore the **frequency** of the excitation pulses can be used to selectively address **qubit** ions that are spatially separated by a distance much less than a wavelength. Here, **frequency**-selective transfer of **qubit** ions between **qubit** states using complex hyperbolic secant pulses is experimentally demonstrated. Transfer efficiencies better than 90% were obtained. Using the complex hyperbolic secant pulses it was also possible to create two groups of ions, absorbing at specific **frequencies**, where 85% of the ions at one of the **frequencies** was shifted out of resonance with the field when ions in the other **frequency** group were excited. This procedure of selecting interacting ions, called **qubit** distillation, was carried out in preparation for two-**qubit** gate operations in the rare-earth-metal-ion-doped crystals. The techniques for **frequency**-selective state-to-state transfer developed here may be also useful also for other quantum optics and quantum information experiments in these long-coherence-time solid-state systems. ... In optically controlled quantum computers it may be favorable to address different **qubits** using light with different **frequencies**, since the optical diffraction does not then limit the distance between **qubits**. Using **qubits** that are close to each other enables **qubit**-**qubit** interactions and gate operations that are strong and fast in comparison to **qubit**-environment interactions and decoherence rates. However, as **qubits** are addressed in **frequency** space, great care has to be taken when designing the laser pulses, so that they perform the desired operation on one **qubit**, without affecting other **qubits**. Complex hyperbolic secant pulses have theoretically been shown to be excellent for such **frequency**-addressed quantum computing [I. Roos and K. Molmer, Phys. Rev. A 69, 022321 (2004)]—e.g., for use in quantum computers based on optical interactions in rare-earth-metal-ion-doped crystals. The optical transition lines of the rare-earth-metal-ions are inhomogeneously broadened and therefore the **frequency** of the excitation pulses can be used to selectively address **qubit** ions that are spatially separated by a distance much less than a wavelength. Here, **frequency**-selective transfer of **qubit** ions between **qubit** states using complex hyperbolic secant pulses is experimentally demonstrated. Transfer efficiencies better than 90% were obtained. Using the complex hyperbolic secant pulses it was also possible to create two groups of ions, absorbing at specific **frequencies**, where 85% of the ions at one of the **frequencies** was shifted out of resonance with the field when ions in the other **frequency** group were excited. This procedure of selecting interacting ions, called **qubit** distillation, was carried out in preparation for two-**qubit** gate operations in the rare-earth-metal-ion-doped crystals. The techniques for **frequency**-selective state-to-state transfer developed here may be also useful also for other quantum optics and quantum information experiments in these long-coherence-time solid-state systems.

Data types:

Contributors: Howan Leung, Cannon X.L. Zhu, Danny T.M. Chan, Wai S. Poon, Lin Shi, Vincent C.T. Mok, Lawrence K.S. Wong

Date: 2015-01-01

High-**frequency** **oscillations**...An example of the implantation schedule (patient #1) demonstrating areas with conventional **frequency** ictal patterns, ictal high-**frequency** **oscillations**, hyperexcitability, and radiological lesions.
...An example of the implantation schedule (patient #7) demonstrating areas with conventional **frequency** ictal patterns, ictal high-**frequency** **oscillations**, hyperexcitability, and radiological lesions.
...High-**frequency** **oscillations** (HFOs, 80–500Hz) from intracranial electroencephalography (EEG) may represent a biomarker of epileptogenicity for epilepsy. We explored the relationship between ictal HFOs and hyperexcitability with a view to improving surgical outcome....Summary table for statistical analysis. HFO=high **frequency** **oscillations**, CFIP=conventional **frequency** ictal patterns.
... High-**frequency** **oscillations** (HFOs, 80–500Hz) from intracranial electroencephalography (EEG) may represent a biomarker of epileptogenicity for epilepsy. We explored the relationship between ictal HFOs and hyperexcitability with a view to improving surgical outcome.

Data types:

Contributors: Feurer, Thomas, Bernhard, Christof, Bessire, Bänz, Stefanov, André

Date: 2013-01-01

We demonstrate the creation, characterization, and manipulation of **frequency**-entangled qudits by shaping the energy spectrum of entangled photons. The generation of maximally entangled qudit states is verified up to dimension d=4 through tomographic quantum-state reconstruction. Subsequently, we measure Bell parameters for **qubits** and qutrits as a function of their degree of entanglement. In agreement with theoretical predictions, we observe that for qutrits the Bell parameter is less sensitive to a varying degree of entanglement than for **qubits**. For **frequency**-entangled photons, the dimensionality of a qudit is ultimately limited by the bandwidth of the pump laser and can be on the order of a few millions. ... We demonstrate the creation, characterization, and manipulation of **frequency**-entangled qudits by shaping the energy spectrum of entangled photons. The generation of maximally entangled qudit states is verified up to dimension d=4 through tomographic quantum-state reconstruction. Subsequently, we measure Bell parameters for **qubits** and qutrits as a function of their degree of entanglement. In agreement with theoretical predictions, we observe that for qutrits the Bell parameter is less sensitive to a varying degree of entanglement than for **qubits**. For **frequency**-entangled photons, the dimensionality of a qudit is ultimately limited by the bandwidth of the pump laser and can be on the order of a few millions.

Data types:

Contributors: Yan, Ying, Li, Yichao, Kinos, Adam, Walther, Andreas, Shi, Chunyan, Rippe, Lars, Moser, Joel, Kröll, Stefan, Chen, Xi

Date: 2019-03-18

High-fidelity **qubit** initialization is of significance for efficient error correction in fault tolerant quantum algorithms. Combining two best worlds, speed and robustness, to achieve high-fidelity state preparation and manipulation is challenging in quantum systems, where **qubits** are closely spaced in **frequency**. Motivated by the concept of shortcut to adiabaticity, we theoretically propose the shortcut pulses via inverse engineering and further optimize the pulses with respect to systematic errors in **frequency** detuning and Rabi **frequency**. Such protocol, relevant to **frequency** selectivity, is applied to rare-earth ions **qubit** system, where the excitation of **frequency**-neighboring **qubits** should be prevented as well. Furthermore, comparison with adiabatic complex hyperbolic secant pulses shows that these dedicated initialization pulses can reduce the time that ions spend in the excited state by a factor of 6, which is important in coherence time limited systems to approach an error rate manageable by quantum error correction. The approach may also be applicable to superconducting **qubits**, and any other systems where **qubits** are addressed in **frequency**. ... High-fidelity **qubit** initialization is of significance for efficient error correction in fault tolerant quantum algorithms. Combining two best worlds, speed and robustness, to achieve high-fidelity state preparation and manipulation is challenging in quantum systems, where **qubits** are closely spaced in **frequency**. Motivated by the concept of shortcut to adiabaticity, we theoretically propose the shortcut pulses via inverse engineering and further optimize the pulses with respect to systematic errors in **frequency** detuning and Rabi **frequency**. Such protocol, relevant to **frequency** selectivity, is applied to rare-earth ions **qubit** system, where the excitation of **frequency**-neighboring **qubits** should be prevented as well. Furthermore, comparison with adiabatic complex hyperbolic secant pulses shows that these dedicated initialization pulses can reduce the time that ions spend in the excited state by a factor of 6, which is important in coherence time limited systems to approach an error rate manageable by quantum error correction. The approach may also be applicable to superconducting **qubits**, and any other systems where **qubits** are addressed in **frequency**.

Data types:

Contributors: Naik, Ravi Kaushik

Date: 2018-01-01

In this thesis, we examine an extension of circuit quantum electrodynamics (QED), cavity QED using superconducting circuits, that utilizes multimode cavities as a resource for quantum information processing. We focus on the issue of **qubit** connectivity in the processors, with an ideal processor having random access -- the ability of arbitrary **qubit** pairs to interact directly. Here, we implement a random access superconducting quantum information processor, demonstrating universal operations on a nine-**qubit** memory, with a Josephson junction transmon circuit serving as the central processor. The quantum memory is a multimode cavity, using the eigenmodes of a linear array of coupled superconducting resonators. We selectively stimulate vacuum Rabi **oscillations** between the transmon and individual eigenmodes through parametric flux modulation of the transmon **frequency**. Utilizing these **oscillations**, we perform a universal set of quantum gates on 38 arbitrary pairs of modes and prepare multimode entangled states, all using only two control lines. We thus achieve hardware-efficient random access multi-**qubit** control. We also explore a novel design for creating long-lived 3D cavity memories compatible with this processor. Dubbed the ``quantum flute'', this design is monolithic, avoiding the loss suffered by cavities with a seam between multiple parts. We demonstrate the ability to manipulate the spectrum of a multimode cavity and also measure photon lifetimes of 0.5-1.3 ms for 21 modes. The combination of long-lived quantum memories with random access makes for a promising architecture for quantum computing moving forward. ... In this thesis, we examine an extension of circuit quantum electrodynamics (QED), cavity QED using superconducting circuits, that utilizes multimode cavities as a resource for quantum information processing. We focus on the issue of **qubit** connectivity in the processors, with an ideal processor having random access -- the ability of arbitrary **qubit** pairs to interact directly. Here, we implement a random access superconducting quantum information processor, demonstrating universal operations on a nine-**qubit** memory, with a Josephson junction transmon circuit serving as the central processor. The quantum memory is a multimode cavity, using the eigenmodes of a linear array of coupled superconducting resonators. We selectively stimulate vacuum Rabi **oscillations** between the transmon and individual eigenmodes through parametric flux modulation of the transmon **frequency**. Utilizing these **oscillations**, we perform a universal set of quantum gates on 38 arbitrary pairs of modes and prepare multimode entangled states, all using only two control lines. We thus achieve hardware-efficient random access multi-**qubit** control. We also explore a novel design for creating long-lived 3D cavity memories compatible with this processor. Dubbed the ``quantum flute'', this design is monolithic, avoiding the loss suffered by cavities with a seam between multiple parts. We demonstrate the ability to manipulate the spectrum of a multimode cavity and also measure photon lifetimes of 0.5-1.3 ms for 21 modes. The combination of long-lived quantum memories with random access makes for a promising architecture for quantum computing moving forward.

Data types:

Contributors: White, William C.

Date: 1916-10-01

... n/a

Data types:

Contributors: Flühmann, Christa

Date: 2019-01-01

Trapped-ions form a promising platform to realize a future large scale quantum computing device. **Qubits** are typically stored in internal electronic states, which are coupled using their joint motion in the trap potential. In this thesis this control paradigm is reversed. The harmonic motion of a trapped calcium ion forms the main subject of studies, which is controlled via the internal electronic states. A number of new techniques are introduced and examined, primarily based on the implementation of modular variable measurements. These are realized combining an internal state dependent optical dipole force with readout of the internal states. Modular measurements are used to investigate large "Schrödinger cat'' states of the ion's motion, to violate Leggett-Garg tests of macroscopic realism, and finally to realize a logical **qubit** encoded in an error-correcting code based on the trapped-ion **oscillator**. The latter offers an alternative to the standard **qubit** based quantum information processing approach, which when embedded in systems of coupled **oscillators** could lead to a large-scale quantum computer. Measurements of a particle's modular position and momentum have been the focus of various discussions of foundational quantum mechanics. Such modular measurements of the trapped-ion's motion are studied in depth in this thesis, in particular their ability to commute, which forms a key element for the latter work on error-correcting codes. Here we make use of the ability to investigate sequences of measurements on a single harmonic **oscillator**, and study correlations between their results, as well as quantum measurement disturbances between the measurements. In order to achieve the major results of the thesis, it was necessary to characterize and control multiple wave packets in phase space. On the characterization side, the need to cope with states with high energy occupations led to the development of multiple new methods for quantum state tomography, including the use of a squeezed eigenstate basis, and the direct extraction of the characteristic function of the **oscillator** using state-dependent forces. These were used to analyze some of the largest **oscillator** "Schrödinger cat'' states which have been produced to date. The main result of this thesis is encoding and full control of a logical **qubit** in the motional **oscillator** space using a code proposed 18 years ago by Gottesman, Kitaev and Preskill. Logical code states are realized and manipulated using sequences of up to five modular measurements applied to an ion initially prepared in a squeezed motional state. Such sequences realize superpositions of multiple squeezed wave packets, which form the code words. The usage of the **oscillator** enables to encode and in principle correct a logical **qubit** within a single trapped ion, which when compared to typical **qubit**-array based approaches simplifies control and hardware. While the discussion above focuses on the new physics in this thesis, in addition the work required technical upgrades to the system, improving control of both **qubit** and **oscillator**. These form important components which have impact on all experiments in our setup, beyond the bounds of the current thesis.,ISBN:5800134927809, ... Trapped-ions form a promising platform to realize a future large scale quantum computing device. **Qubits** are typically stored in internal electronic states, which are coupled using their joint motion in the trap potential. In this thesis this control paradigm is reversed. The harmonic motion of a trapped calcium ion forms the main subject of studies, which is controlled via the internal electronic states. A number of new techniques are introduced and examined, primarily based on the implementation of modular variable measurements. These are realized combining an internal state dependent optical dipole force with readout of the internal states. Modular measurements are used to investigate large "Schrödinger cat'' states of the ion's motion, to violate Leggett-Garg tests of macroscopic realism, and finally to realize a logical **qubit** encoded in an error-correcting code based on the trapped-ion **oscillator**. The latter offers an alternative to the standard **qubit** based quantum information processing approach, which when embedded in systems of coupled **oscillators** could lead to a large-scale quantum computer. Measurements of a particle's modular position and momentum have been the focus of various discussions of foundational quantum mechanics. Such modular measurements of the trapped-ion's motion are studied in depth in this thesis, in particular their ability to commute, which forms a key element for the latter work on error-correcting codes. Here we make use of the ability to investigate sequences of measurements on a single harmonic **oscillator**, and study correlations between their results, as well as quantum measurement disturbances between the measurements. In order to achieve the major results of the thesis, it was necessary to characterize and control multiple wave packets in phase space. On the characterization side, the need to cope with states with high energy occupations led to the development of multiple new methods for quantum state tomography, including the use of a squeezed eigenstate basis, and the direct extraction of the characteristic function of the **oscillator** using state-dependent forces. These were used to analyze some of the largest **oscillator** "Schrödinger cat'' states which have been produced to date. The main result of this thesis is encoding and full control of a logical **qubit** in the motional **oscillator** space using a code proposed 18 years ago by Gottesman, Kitaev and Preskill. Logical code states are realized and manipulated using sequences of up to five modular measurements applied to an ion initially prepared in a squeezed motional state. Such sequences realize superpositions of multiple squeezed wave packets, which form the code words. The usage of the **oscillator** enables to encode and in principle correct a logical **qubit** within a single trapped ion, which when compared to typical **qubit**-array based approaches simplifies control and hardware. While the discussion above focuses on the new physics in this thesis, in addition the work required technical upgrades to the system, improving control of both **qubit** and **oscillator**. These form important components which have impact on all experiments in our setup, beyond the bounds of the current thesis.,ISBN:5800134927809,

Data types: