Quantum theory of diffusion-accelerated remote transfer

Daniel L. Van Gent

We report experiments in which two indium foils were quantum entangled via photoexcitation of stable 115In to radioactive 115mIn by utilizing Bremsstrahlung gamma photons produced by a Varian Compact Linear Accelerator (CLINAC). After photo-excitation, remote triggering of the "master" foil with low energy gamma photons, yielded stimulated emissions of 336 keV gamma photons from quantum entangled 115mIn in the "slave" foil located up to 1600 m away from the "master" foil. These experiments strongly demonstrate that useful quantum information can be transferred through quantum channels via modulation of quantum noise (accelerated radioactive decay of 115mIn metastable nuclei). Thus, this modality of QE transmission is fundamentally different from optical QE information transfer via quantum entangled space "q-bits" as developed by information theorists for quantum channel information transfer. Additionally, there is no obvious potential for signal degradation with increasing distance nor the problems associated with misalignment of optical information transfer systems.

J. Amran Sussmann

Peer Fisser

This report presents theoretical predictions of the behavior of spin polarized systems in motion. More specifically, it looks at systems which have been configured to contain only two specific spin states. When a magnetic field is applied the two different "species" undergo different accelerations, resulting in interspecies collisions that, due to momentum transfer between the spin states, tend the system to an equilibrium with equal drift velocities of each spin species. This drag phenomenon is the primary focus of this report. By using the Boltzmann equation we predict quantum effects within a range of drift velocities around zero. The boson system portrays Bose-enhancement (significantly higher momentum transfer), while the fermion system manifests Pauli blocking (significantly lower momentum transfer). More remarkably, the boson-fermion system shows its own unique kind of blocking effect. Attention is also given to diffusion. The consideration of the system close to equilibrium allows for a derivation of the diffusion constant by using the Einstein relation.

R. L. Hudson, Kalyanapuram Rangachari Parthasarathy

Sushanta Dattagupta, Sanjay Puri

Kentaro Heya, Timothy Phung, Moein Malekakhlagh +8 more

High-fidelity, meter-scale microwave interconnects between superconducting quantum processor modules are a key technology for extending the system size beyond constraints imposed by device manufacturing equipment, yield, and signal delivery. Although tomographic experiments have been used in previous demonstrations for benchmarking remote state transfer between modules, they do not reliably separate state preparation and measurement (SPAM) error from the error per state transfer. Recent developments based on randomized benchmarking provide a compatible theory for separating these two errors. In this Letter, we present a module-to-module interconnect based on tunable-coupling qubits and benchmark, in a SPAM-error-tolerant manner enabled by a frame-tracking technique, a remote state transfer fidelity of 98.8% across a 60 cm-long coplanar waveguide (CPW). The state transfer is implemented via a superadiabatic transitionless driving method, which suppresses intermediate excitation in the internal modes of the CPW. We further propose and construct a remote cnot gate between modules, composed of local controlled-Z (CZ) gates in each module and remote state transfers, and report a gate fidelity of 93.3% using the randomized benchmarking method. The remote cnot construction and benchmarking we present provide a way to fully characterize the module-to-module link operation and standardize reporting fidelity, analogous to randomized benchmarking protocols for other quantum gates.