Filter Results

3933 results

Data Types:

- Document

Data Types:

- Document

Since the dawn of quantum information science, laser-cooled trapped atomic ions have been one of the most compelling systems for the physical realization of a quantum computer. By applying **qubit** state dependent forces to the ions, their collective motional modes can be used as a bus to realize entangling quantum gates. Ultrafast state-dependent kicks [1] can provide a universal set of quantum logic operations, in conjunction with ultrafast single **qubit** rotations [2], which uses only ultrafast laser pulses. This may present a clearer route to scaling a trapped ion processor [3]. In addition to the role that spin-dependent kicks (SDKs) play in quantum computation, their utility in fundamental quantum mechanics research is also apparent. In this thesis, we present a set of experiments which demonstrate some of the principle properties of SDKs including ion motion independence (we demonstrate single ion thermometry from the ground state to near room temperature and the largest Schrodinger cat state ever created in an **oscillator**), high speed operations (compared with conventional atom-laser interactions), and multi-**qubit** entanglement operations with speed that is not fundamentally limited by the trap **oscillation** **frequency**. We also present a method to provide higher stability in the radial mode ion **oscillation** **frequencies** of a linear radiofrequency (rf) Paul trap--a crucial factor when performing operations on the rf-sensitive modes. Finally, we present the highest atomic position sensitivity measurement of an isolated atom to date of ~0.5 nm Hz^(-1/2) with a minimum uncertainty of 1.7 nm using a 0.6 numerical aperature (NA) lens system, along with a method to correct aberrations and a direct position measurement of ion micromotion (the inherent **oscillations** of an ion trapped in an **oscillating** rf field). This development could be used to directly image atom motion in the quantum regime, along with sensing forces at the yoctonewton [10^(-24) N)] scale for gravity sensing, and 3D imaging of atoms from static to higher **frequency** motion. These ultrafast atomic **qubit** manipulation tools demonstrate inherent advantages over conventional techniques, offering a fundamentally distinct regime of control and speed not previously achievable.

Data Types:

- Collection

6-The electron **oscillating** period as functions of the temperature and the cyclotron **frequency** in triangular quantum dot **qubit** under an electric field.docx... Fig.4. A-Function relationship between the first excited state energy and the temperature and the electron-phonon coupling constant for different cyclotron **frequencies** and ,,,; B-Function relationship between the first excited energy and the temperature and the electric field strength for different cyclotron **frequencies** and ,,,; C-Function relationship between the first excited energy and the temperature and the confinement length for different cyclotron **frequencies** and ,,,; D-Function relationship between the first excited energy and of the temperature and the Coulomb impurity potential for different cyclotron **frequencies** and ,,,... Fig.1. A-Function relationship between the ground state energy and the temperature and the cyclotron **frequency** for different electron-phonon coupling constants and ,,, ; B-Function relationship between the ground state energy and the temperature and the cyclotron **frequency** for different electric field strengths and ,,,; C-Function relationship between the ground state energy and the temperature and the cyclotron **frequency** for different confinement lengths and ,,,; D-Function relationship between the ground state energy and the temperature and the cyclotron **frequency** for different Coulomb impurity potentials and ,,,... Fig.6. A-The electron **oscillation** period as functions of the temperature and the cyclotron **frequency** for different electron-phonon coupling constants and ,,,; B-The electron **oscillation** period as functions of the temperature and the cyclotron **frequency** for different electric field strengths and,,,; C-The electron **oscillation** period as functions of the temperature and the cyclotron **frequency** for different confinement lengths and ,,,; D-The electron **oscillation** period as functions of the temperature and the cyclotron **frequency** for different Coulomb impurity potentials and ,,,... 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... Fig.7. A-The electron **oscillation** period as functions of the temperature and the electron-phonon coupling constant for different cyclotron **frequencies** and ,,,; B-The electron **oscillation** period as functions of the temperature and the electric field strength for different cyclotron **frequencies** and ,,,; C-The electron **oscillation** period as functions of the temperature and the confinement length for different cyclotron **frequencies** and ,,,; D-The electron **oscillation** period as functions of the temperature and the Coulomb impurity potential for different cyclotron **frequencies** and ,,,... 1-The ground state energy as functions of the temperature and the cyclotron **frequency** in triangular quantum dot **qubit** under an electric field.docx... Fig.3. A-Function relationship between the ground state energy and the temperature and the electron-phonon coupling constant for different cyclotron **frequencies** and ,,,; B-Function relationship between the ground state energy and the temperature and the electric field strength for different cyclotron **frequencies** and ,,,; C-Function relationship between the ground state energy and of the temperature and the confinement length for different cyclotron **frequencies** and ,,,; D-Function relationship between the ground state energy and the temperature and the Coulomb impurity potential for different cyclotron **frequencies** and ,,,

Data Types:

- Dataset
- Document

Superconducting **qubits**

Data Types:

- Collection

While the advanced coherent control of **qubits** is now routinely carried out in low **frequency** (GHz) systems like single spins, it is far more challenging to achieve for two-level systems in the optical domain. This is because the latter evolve typically in the THz range, calling for tools of ultrafast, coherent, nonlinear optics. Using four-wave mixing micro-spectroscopy, we here measure the optically driven Bloch vector dynamics of a single exciton confined in a semiconductor quantum dot. In a combined experimental and theoretical approach, we reveal the intrinsic Rabi **oscillation** dynamics by monitoring both central exciton quantities, i.e., its occupation and the microscopic coherence, as resolved by the four-wave mixing technique. In the **frequency** domain this **oscillation** generates the Autler-Townes splitting of the light-exciton dressed states, directly seen in the four-wave mixing spectra. We further demonstrate that the coupling to acoustic phonons strongly influences the FWM dynamics on the picosecond timescale, because it leads to transitions between the dressed states.

Data Types:

- Collection

While the advanced coherent control of **qubits** is now routinely carried out in low **frequency** (GHz) systems like single spins, it is far more challenging to achieve for two-level systems in the optical domain. This is because the latter evolve typically in the THz range, calling for tools of ultrafast, coherent, nonlinear optics. Using four-wave mixing micro-spectroscopy, we here measure the optically driven Bloch vector dynamics of a single exciton confined in a semiconductor quantum dot. In a combined experimental and theoretical approach, we reveal the intrinsic Rabi **oscillation** dynamics by monitoring both central exciton quantities, i.e., its occupation and the microscopic coherence, as resolved by the four-wave mixing technique. In the **frequency** domain this **oscillation** generates the Autler-Townes splitting of the light-exciton dressed states, directly seen in the four-wave mixing spectra. We further demonstrate that the coupling to acoustic phonons strongly influences the FWM dynamics on the picosecond timescale, because it leads to transitions between the dressed states.

Data Types:

- Collection

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:

- Document

We implement distinct quantum gates in parallel on two entangled **frequency**-bin **qubits** for the first time. Our basic quantum operation controls the spectral overlap between adjacent **frequency** bins, allowing us to observe **frequency**-bin Hong-Ou-Mandel interference with a visibility of 0.971±0.007, a record for two photons of different colors. By integrating this tunability with **frequency** parallelization, we synthesize independent gates on entangled **qubits** in the same optical fiber and flip their spectral correlations. The ultralow noise of our gates preserves entanglement purity, as evidenced by a 9.8σ violation of an entropic separability bound. Our results constitute the first closed, user-defined gates on **frequency**-bin **qubits** in parallel, with application to the development of **frequency**-based quantum information processing.

Data Types:

- Collection

We implement distinct quantum gates in parallel on two entangled **frequency**-bin **qubits** for the first time. Our basic quantum operation controls the spectral overlap between adjacent **frequency** bins, allowing us to observe **frequency**-bin Hong-Ou-Mandel interference with a visibility of 0.971±0.007, a record for two photons of different colors. By integrating this tunability with **frequency** parallelization, we synthesize independent gates on entangled **qubits** in the same optical fiber and flip their spectral correlations. The ultralow noise of our gates preserves entanglement purity, as evidenced by a 9.8σ violation of an entropic separability bound. Our results constitute the first closed, user-defined gates on **frequency**-bin **qubits** in parallel, with application to the development of **frequency**-based quantum information processing.

Data Types:

- Collection