The New Age of Accounting Regulation Canada and the United States

This paper reviews major differences between the accounting regulatory systems in Canada and the United States. In the U.S., the Sarbanes-Oxley Act of 2002 governs responsibilities of management, auditors, and Boards of Directors related to internal control over financial reporting. In Canada, a series of Multilateral Instruments under provincial jurisdiction serves similar objectives. As compared to the U.S., the Canadian system is more decentralized and principles-based allowing a greater degree of responsibility to the accounting profession for standard setting and oversight. The Canadian approach has resulted in weaker regulation, slower implementation, and greater influence by the accounting profession. These findings imply that accounting regulations should be tailored to fit the political and institutional structures of the adopting country

Dissipation signatures of the normal and superfluid phases in torsion pendulum experiments with 3He in aerogel

We present data for energy dissipation factor (Q^{-1}) over a broad temperature range at various pressures of a torsion pendulum setup used to study 3He confined in a 98% open silica aerogel. Values for Q^{-1} above T_c are temperature independent and have a weak pressure dependence. Below T_c, a deliberate axial compression of the aerogel by 10% widens the range of metastability for a superfluid Equal Spin Pairing (ESP) state; we observe this ESP phase on cooling and the B phase on warming over an extended temperature region. While the dissipation for the B phase tends to zero as T goes to 0, Q^{-1} exhibits a peak value greater than that at T_c at intermediate temperatures. Values for Q^{-1} in the ESP phase are consistently higher than in the B phase and are proportional to \rho_s/\rho until the ESP to B phase transition is attained. We apply a viscoelastic collision-drag model, which couples the motion of the helium and the aerogel through a frictional relaxation time \tau_f. Our dissipation data is not sensitive to the damping due to the presumed small but non-zero value of \tau_f. The result is that an additional mechanism to dissipate energy not captured in the collision-drag model and related to the emergence of the superfluid order must exist. The extra dissipation below T_c is possibly associated with mutual friction between the superfluid phases and the clamped normal fluid. The pressure dependence of the measured dissipation in both superfluid phases is likely related to the pressure dependence of the gap structure of the "dirty" superfluid. The large dissipation in the ESP state is consistent with the phase being the A or the Polar with the order parameter nodes oriented in the plane of the cell and perpendicular to the aerogel anisotropy axis.Comment: 12 pages, 7 figure

Strong Coupling Corrections to the Ginzburg-Landau Theory of Superfluid ^{3}He

In the Ginzburg-Landau theory of superfluid $^{3}$He, the free energy is expressed as an expansion of invariants of a complex order parameter. Strong coupling effects, which increase with increasing pressure, are embodied in the set of coefficients of these order parameter invariants\cite{Leg75,Thu87}. Experiments can be used to determine four independent combinations of the coefficients of the five fourth order invariants. This leaves the phenomenological description of the thermodynamics near $T_{c}$ incomplete. Theoretical understanding of these coefficients is also quite limited. We analyze our measurements of the magnetic susceptibility and the NMR frequency shift in the $B$-phase which refine the four experimental inputs to the phenomenological theory. We propose a model based on existing experiments, combined with calculations by Sauls and Serene\cite{Sau81} of the pressure dependence of these coefficients, in order to determine all five fourth order terms. This model leads us to a better understanding of the thermodynamics of superfluid $^{3}$He in its various states. We discuss the surface tension of bulk superfluid $^{3}$He and predictions for novel states of the superfluid such as those that are stabilized by elastic scattering of quasiparticles from a highly porous silica aerogel.Comment: 9 pages, 7 figures, 2 table

Mass coupling and Q−1ofimpurity−limitednormalQ^{-1} of impurity-limited normal ^3$He in a torsion pendulum

We present results of the $Q^{-1}$ and period shift, $\Delta P$, for $^3$He confined in a 98% nominal open aerogel on a torsion pendulum. The aerogel is compressed uniaxially by 10% along a direction aligned to the torsion pendulum axis and was grown within a 400 $\mu$m tall pancake (after compression) similar to an Andronikashvili geometry. The result is a high $Q$ pendulum able to resolve $Q^{-1}$ and mass coupling of the impurity-limited $^3$He over the whole temperature range. After measuring the empty cell background, we filled the cell above the critical point and observe a temperature dependent period shift, $\Delta P$, between 100 mK and 3 mK that is 2.9$$ of the period shift (after filling) at 100 mK. The $Q^{-1}$ due to the $^3$He decreases by an order of magnitude between 100 mK and 3 mK at a pressure of $0.14\pm0.03$ bar. We compare the observable quantities to the corresponding calculated $Q^{-1}$ and period shift for bulk $^3$He.Comment: 8 pages, 3 figure

Free-space coupling and characterization of transverse bulk phonon modes in a quantum acoustic device

Transverse bulk phonons in a multimode integrated quantum acoustic device are excited and characterized via their free-space coupling to a three-dimensional (3D) microwave cavity. These bulk acoustic modes are defined by the geometry of the Y-cut lithium niobate substrate in which they reside and couple to the cavity electric field via a large dipole antenna, with an interaction strength on the order of the cavity line-width. Using finite element modeling (FEM) we determine that the bulk phonons excited by the cavity field have a transverse polarization with a shear velocity matching previously reported values. We demonstrate how the coupling between these transverse acoustic modes and the electric field of the 3D cavity depends on the relative orientation of the device dipole, with a coupling persisting to room temperature. Our study demonstrates the versatility of 3D microwave cavities for mediating contact-less coupling to quantum, and classical, piezoacoustic devices.Comment: 5 pages, 4 figure

Quantum acoustic Fano interference of surface phonons

Quantum acoustic systems, which integrate surface or bulk phonons with superconducting qubits, offer a unique opportunity to investigate phononic $interference$ and $scattering$ processes in the quantum regime. In particular the interaction between a superconducting qubit and a phononic oscillator allows the qubit to sense the oscillator's excitation spectrum and underlying interference effects. Here we present measurements revealing Fano interference of a resonantly trapped piezoelectric surface acoustic wave (SAW) mode with a broad continuum of surface phonons in a system consisting of a SAW resonator coupled to a superconducting qubit. The experiments highlight the existence of additional weakly coupled mechanical modes and their influence on the qubit-phonon interaction and underscore the importance of phononic interference in quantum acoustic architectures that have been proposed for quantum information processing applications.Comment: 7 pages, 5 figures. Updated title and abstrac

Phononic bath engineering of a superconducting qubit

Phonons, the ubiquitous quanta of vibrational energy, play a vital role in the performance of many quantum technologies. Coupling to well-defined phonon modes allows for highly-connected multi-qubit gates in ion trap architectures as well as the generation of entangled states in systems of superconducting qubits. Even when the phonons take the form of a large dissipative bath, an irreversible flow of heat allows for state initialization critical to the function of laser systems and the operation of optically active spin qubits. Conversely, unintended coupling to phonons has been shown to degrade qubit performance by generating decohering quasiparticles and leading to correlated errors in superconducting qubit systems. Regardless of whether a phononic bath plays an enabling or deleterious role, it is typically intrinsic to the system and does not admit specific control over its spectral properties, nor the possibility of engineering aspects of its dissipation to be used as a resource. Here we show that by precisely designing and controlling the coupling of a superconducting qubit to phononic degrees of freedom allows a new type of quantum control over superconducting circuits. By shaping the loss spectrum of the qubit via its coupling to a bath of lossy piezoelectric surface acoustic wave phonons, we are able to prepare and stabilize arbitrary qubit states. Additionally, we find that the presence of the energy-dependent loss imparted onto the qubit by the phonons is well-described by a master equation treatment of the composite system, with excellent agreement in both the qubit dynamics as well as its steady state. Our results demonstrate the ability of engineered phononic dissipation to achieve highly efficient qubit control.Comment: 18 pages, 5 figures, 1 table, main text and S

Phase diagram of superfluid 3He in "nematically ordered" aerogel

Results of experiments with liquid 3He immersed in a new type of aerogel are described. This aerogel consists of Al2O3 strands which are nearly parallel to each other, so we call it as a "nematically ordered" aerogel. At all used pressures a superfluid transition was observed and a superfluid phase diagram was measured. Possible structures of the observed superfluid phases are discussed.Comment: 6 pages, 8 figures. Submitted to Pis'ma v ZhETF (JETP Letters