Optomechanical approach to controlling the temperature and chemical potential of light

Massless particles, including photons, are not governed by particle conservation law during their typical interaction with matter even at low energies, and thus have no chemical potential. However, in driven systems, near equilibrium dynamics can lead to equilibration of photons with a finite number, describable using an effective chemical potential [M. Hafezi et al., Phys. Rev. B 92, 174305 (2015)]. Here we build upon this general concept with an implementation appropriate for a photon-based quantum simulator. We consider how laser cooling of a well-isolated mechanical mode can provide an effective low-frequency bath for the quantum simulator system. We show that the use of auxiliary photon modes, coupled by the mechanical system, enables control of both the chemical potential and temperature of the resulting photonic quantum simulator's grand canonical ensemble

Dynamic suppression of Rayleigh light scattering in dielectric resonators

The ultimate limits of performance for any classical optical system are set by sub-wavelength fluctuations within the host material, that may be frozen-in or even dynamically induced. The most common manifestation of such sub-wavelength disorder is Rayleigh light scattering, which is observed in nearly all wave-guiding technologies today and can lead to both irreversible radiative losses as well as undesirable intermodal coupling. While it has been shown that backscattering from disorder can be suppressed by breaking time-reversal symmetry in magneto-optic and topological insulator materials, common optical dielectrics possess neither of these properties. Here we demonstrate an optomechanical approach for dynamically suppressing Rayleigh backscattering within dielectric resonators. We achieve this by locally breaking time-reversal symmetry in a silica resonator through a Brillouin scattering interaction that is available in all materials. Near-complete suppression of Rayleigh backscattering is experimentally confirmed through three independent measurements -- the reduction of the back-reflections caused by scatterers, the elimination of a commonly seen normal-mode splitting effect, and by measurement of the reduction in intrinsic optical loss. More broadly, our results provide new evidence that it is possible to dynamically suppress Rayleigh backscattering within any optical dielectric medium, for achieving robust light propagation in nanophotonic devices in spite of the presence of scatterers or defects

Electro-optomechanical equivalent circuits for quantum transduction

Using the techniques of optomechanics, a high-$Q$ mechanical oscillator may serve as a link between electromagnetic modes of vastly different frequencies. This approach has successfully been exploited for the frequency conversion of classical signals and has the potential of performing quantum state transfer between superconducting circuitry and a traveling optical signal. Such transducers are often operated in a linear regime, where the hybrid system can be described using linear response theory based on the Heisenberg-Langevin equations. While mathematically straightforward to solve, this approach yields little intuition about the dynamics of the hybrid system to aid the optimization of the transducer. As an analysis and design tool for such electro-optomechanical transducers, we introduce an equivalent circuit formalism, where the entire transducer is represented by an electrical circuit. Thereby we integrate the transduction functionality of optomechanical systems into the toolbox of electrical engineering allowing the use of its well-established design techniques. This unifying impedance description can be applied both for static (DC) and harmonically varying (AC) drive fields, accommodates arbitrary linear circuits, and is not restricted to the resolved-sideband regime. Furthermore, by establishing the quantized input-output formalism for the equivalent circuit, we obtain the scattering matrix for linear transducers using circuit analysis, and thereby have a complete quantum mechanical characterization of the transducer. Hence, this mapping of the entire transducer to the language of electrical engineering both sheds light on how the transducer performs and can at the same time be used to optimize its performance by aiding the design of a suitable electrical circuit

The single device simulation output (stored as ‘output’) is a list of 10 000 dictionaries, holding the simulated data for each point in the plunger voltage space (defined by vectors ‘V_P1_vec’ and ‘V_P2_vec’).

The ‘output’ dictionaries include four variables, as defined in the table.</p

A sample preview output.

A preview of a single dot (left) and of a double dot subregion (right) generated using a QFlow lite build-in function qf.data_preview(). The labels printed above images indicate the actual state, as well as the fraction of each type of state within the given image in the format: [SC, QPC, SD, DD].</p

Data structure.

The generic data structure tree for the data files. The data type is given in square brackets. The simulation output is highlighted in gray. See Tables 2 and 3 for a reference list.</p

Quantum dots from a nanowire.

A) A generic model of a nanowire with 5 gates. The barrier gates, VBi with i = 1, 2, 3 (light gray), are set to a fixed voltage and are used to form islands by confining electron density to certain region. Voltage on the plunger gates, VPj with j = 1, 2 (dark gray), is varied to allow for control of the current flow through the nanowire. B) Potential profile along a nanowire for a double dot system with N1 and N2 denoting the number of electrons on each dot. C) Possible states in the 5-gate device. In the short circuit state the potential profile is below the Fermi level, leading to an unintended current flow. When the potential profile is above the Fermi level, the current flow is blocked (barrier state). By varying the voltage applied to plunger gates in the lower range while keeping the barriers above the Fermi level of the contacts, one can transition between one and two dots.</p

Scanning Localized Magnetic Fields in a Microfluidic Device with a Single Nitrogen Vacancy Center

Nitrogen vacancy (NV) color centers in diamond enable local magnetic field sensing with high sensitivity by optical detection of electron spin resonance (ESR). The integration of this capability with microfluidic technology has a broad range of applications in chemical and biological sensing. We demonstrate a method to perform localized magnetometry in a microfluidic device with a 48 nm spatial precision. The device manipulates individual magnetic particles in three dimensions using a combination of flow control and magnetic actuation. We map out the local field distribution of the magnetic particle by manipulating it in the vicinity of a single NV center and optically detecting the induced Zeeman shift with a magnetic field sensitivity of 17.5 μT Hz^–1/2. Our results enable accurate nanoscale mapping of the magnetic field distribution of a broad range of target objects in a microfluidic device

State distribution.

A) A typical distribution of states in a sample training set (N = 9009). B) A visualization of the performance of the ML algorithm on sample simulated data (N = 1001).</p

The physical parameters of the devices, stored as a dictionary ‘physics’.

Fixed values are given explicitly. Varied parameters, given in angle brackets, were randomly sampled from a Gaussian distribution with the given mean value μ and standard deviation set to 0.05|μ| (unless stated otherwise).</p