The application of the quantum 1/f theory to bulk acoustic wave (BAW) and surface acoustic wave (SAW) quartz resonators has so far been limited to the case of very high Q resonators in which the phonons are coherent throughout the resonator volume. Here the quantum 1/f theory is applied to the general case of an arbitrary coherence length of the phonons, which may be large or small compared with the size of the quartz resonator. This allows to extend the theory for the first time to low-and resonators in which the phonons are localized in a part of the resonator volume. The theory is also extended to include defect scattering along with the phonon scattering case exclusively published so far. The author's recent application of the new Quantum Information Theory Approach (QIT, developed 1996) to Infra Quantum Physics (IQP) explains for the first time the apparent lack of unitarity caused by the entropy increase in the Quantum 1/f Effect (Q1/fE). Indeed, a more rigorous proof of the conventional Q2/fE is offered in this paper, which shows that actually there is pro resultant entropy increase and therefore unitarity is not violated. His new proof involves the concept of von Neumann Quantum Entropy, including the negative conditional entropy concept for quantum entangled states. The Q1/fE was applied to many high-tech systems, in particular to ultra-small electronic devices. The present paper explains how the additional entropy implied by the Q1/fE arises in spite of the entropy-conserving evolution of the system.
The application of the quantum 1/f theory to bulk acoustic wave (BAW) and surface acoustic wave (SAW) quartz resonators has so far been limited to the case of very high Q resonators in which the phonons are coherent throughout the resonator volume. Here the quantum 1/f theory is applied to the general case of an arbitrary coherence length of the phonons, which may be large or small compared with the size of the quartz resonator. This allows to extend the theory for the first time to low-and resonators in which the phonons are localized in a part of the resonator volume. The theory is also extended to include defect scattering along with the phonon scattering case exclusively published so far. The author's recent application of the new Quantum Information Theory Approach (QIT, developed 1996) to Infra Quantum Physics (IQP) explains for the first time the apparent lack of unitarity caused by the entropy increase in the Quantum 1/f Effect (Q1/fE). Indeed, a more rigorous proof of the conventional Q2/fE is offered in this paper, which shows that actually there is pro resultant entropy increase and therefore unitarity is not violated. His new proof involves the concept of von Neumann Quantum Entropy, including the negative conditional entropy concept for quantum entangled states. The Q1/fE was applied to many high-tech systems, in particular to ultra-small electronic devices. The present paper explains how the additional entropy implied by the Q1/fE arises in spite of the entropy-conserving evolution of the system.
The Quantum Information Theory Approach (QIT) explains for the first time the apparent lack of unitarity caused by the entropy increase in the Quantum 1/f Effect (Q1/fE). This allows for a deeper understanding of the quantum 1/f effect, showing no resultant entropy increase and therefore no violation of unitarity in the quantum-mechanical dynamical evolution. This new interpretation involves the von Neumann Quantum Entropy, including the negative conditional entropy concept for quantum entangled states introduced by QIT. The Q1/fE was applied to many high-tech systems, in particular to ultra small electronic devices in nanotechnology. The present paper explains how the additional entropy implied by the observed 1/f noise arises in spite of the entropy-conserving evolution of the system. On this basis, a derivation of the conventional and coherent quantum 1/f effect is given. The latter is derived from a non-relativistic form of the branch-point propagator derived by excluding the long range Coulomb interaction from the interaction hamiltonian. The paper concludes with examples of practical applications in various devices and systems, allowing for a new characterization of high technology.
We demonstrate that Bulk Acoustic Wave (BAW) quartz resonator cooled down to millikelvin temperatures are excellent building blocks for hybrid quantum systems with extremely long coherence times. Two overtones of the longitudinal mode at frequencies of 15.6 and 65.4 MHz demonstrate a maximum f.Q product of 7.8×1016 Hz. With this result, the Q-factor in such devices near the quantum ground state can be four orders of magnitude better than previously attained in other mechanical systems. Tested quartz resonators possess the ultra low acoustic losses crucial for electromagnetic cooling to the phonon ground state.
The conventional Quantum 1/f (Q1/f) Effect is present in any scattering cross section or process rate involving charged particles or current carriers. The present paper shows how bremsstrahlung and decoherence at all frequencies yield macroscopic quantum interference, resulting in probability density fluctuations at all frequencies in the outgoing scattered beam, that are observed as fundamental base-band 1/f noise and as 1/f frequency fluctuations, or phase noise close to carrier, in materials, devices, and resonant or non-resonant systems. We emphasize the role of the phenomenon of quantum decoherence showing that the fundamental, universal 1/f noise is both a phenomenon of decoherence and of the infrared divergence of quantum electrodynamics. This eliminates the last persisting misunderstandings of the Q1/f Theory and of this new field of Infra-quantum Physics. On this basis we give the first universal engineering formulas, applicable for the ultra-low noise optimization of all Hi-Tech applications, of the materials, devices and systems of modern industry, microelectronics, nanotechnology, highest stability resonators, oscillators and clocks, MEMS, and any resonant and non-resonant sensors. Q1/f noise, i.e, the coherent and conventional Q1/f Effects, is a new fundamental aspect of quantum physics, as basic as space and time. In resonators and oscillators, fundamental frequency fluctuations come usually from 1/f fluctuations in the dissipation.
Hybrid systems that couple superconducting qubits to mechanical oscillators facilitate quantum control of individual phonons and have the potential to enable compact, highly coherent quantum memories and processors. To date, however, the utility of hybrid quantum acoustic devices has been limited by poor qubit and mechanical coherence times that are far shorter than those exhibited by their unhybridized counterparts. A primary challenge lies in the intrinsic nature of elastic waves in solids: the slow speed of sound results in a dense spectrum of acoustic modes, making it difficult to prevent spontaneous emission of the qubit into phononic degrees of freedom. In this thesis, I will present a systematic effort to suppress loss mechanisms in superconducting qubits and mechanical resonators in the context of circuit quantum acoustics. I begin by demonstrating the use of crystallographic orientation optimization to passively suppress diffraction losses in narrow-aperture quartz surface acoustic wave (SAW) resonators. We then study the coupling of SAW resonators to a quasi-continuum of bulk acoustic modes; this motivates us to abandon bulk piezoelectric media in favor of bandgap-protected thin-film devices. By fabricating suspended phononic crystal resonators from thin-film quartz, we demonstrate an order-of-magnitude improvement in the coherence of this class of devices. I conclude by presenting preliminary measurements of a new flip-chip architecture for circuit quantum acoustics -- the `acoustic trampoline' -- that is designed to maximize qubit-mechanical coupling while simultaneously suppressing spontaneous acoustic emission.
Phononic resonators are becoming increasingly important in quantum information science, both for applications in quantum computing, communication, and sensing as well as in experiments investigating fundamental physics. Here, we study the decoherence of phonons confined in a surface acoustic wave (SAW) resonator strongly coupled $(g/2\ensuremath{\pi}\ensuremath{\approx}9\phantom{\rule{0.16em}{0ex}}\mathrm{MHz})$ to a superconducting transmon qubit. By comparing experimental data with numerical solutions to the Markovian master equation, we report a surface phononic energy decay rate of ${\ensuremath{\kappa}}_{1}/2\ensuremath{\pi}=480\phantom{\rule{0.16em}{0ex}}\mathrm{kHz}$ and a pure dephasing rate of ${\ensuremath{\kappa}}_{\ensuremath{\phi}}/2\ensuremath{\pi}=180\phantom{\rule{0.16em}{0ex}}\mathrm{kHz}$. These rates are in good agreement with the level of decoherence we extract from qubit-assisted spectroscopic measurements of the SAW resonator. We additionally find that the timescales over which coherent driven dynamics and decoherence occur are comparable, highlighting the need to model the composite device as an open quantum system. We discuss possible sources of decoherence in SAW-based quantum acoustic devices and the application of these devices in future quantum acoustic dissipation engineering experiments. The decoherence characterization techniques we employ are broadly applicable for investigating and benchmarking the effects of loss and dephasing on mechanical resonators in the quantum regime.
We propose a scheme to implement the phonon antibunching and phonon blockade in a circuit quantum acoustodynamical system containing two surface acoustic wave (SAW) resonators coupled to a superconducting qubit. In the cases of driving only one SAW resonator and two SAW resonators, we investigate the phonon statistics by numerically calculating the second-order correlation function. It is found that, when only one SAW cavity is resonantly driven, the phonon antibunching effect can be achieved even when the qubit-phonon coupling strength is smaller than the decay rates of acoustic cavities. This result physically originates from the quantum interference between super-Poissonian statistics and Poissonian statistics of phonons. In particular, when the two SAW resonators are simultaneously driven under the mechanical resonant condition, the phonon antibunching effect can be significantly enhanced, which ultimately allows for the generation of a phonon blockade. Moreover, the obtained phonon blockade can be optimized by regulating the intensity ratio of the two SAW driving fields. In addition, we also discuss in detail the effect of system parameters on the phonon statistics. Our work provides an alternative way for manipulating and controlling the nonclassical effects of SAW phonons. It may inspire the engineering of new SAW-based phonon devices and extend their applications in quantum information processing.