The Quantum Eraser Paradox

The Delayed-Choice Quantum Eraser experiment is commonly interpreted as implying that in quantum mechanics a choice made at one time can influence an earlier event. We here suggest an extension of the experiment that results in a paradox when interpreted using a local realist interpretation combined with backward causation ("retrocausality"). We argue that resolving the paradox requires giving up the idea that, in quantum mechanics, a choice can influence the past, and that it instead requires a violation of Statistical Independence without retrocausality. We speculate what the outcome of the experiment would be.Comment: 8 pages, 6 figures. v2: minor fixes, references adde

Reply to arXiv:2111.13357 ("The Quantum Eraser Non-Paradox'')

In a recent criticism (arXiv:2111.13357) of our paper arXiv:2111.09347, Drezet argues that we have forgotten to consider superpositions of detector eigenstates. However, such superpositions do not occur in the models our paper is concerned with. We also note that no one has ever observed such detector superpositions.Comment: 1 pages, no figure

Frequency Domain Multiplexing for MKIDs: Comparing the Xilinx ZCU111 RFSoC with their new 2x2 RFSoC board

The Xilinx ZCU111 Radio Frequency System on Chip (RFSoC) is a promising solution for reading out large arrays of microwave kinetic inductance detectors (MKIDs). The board boasts eight on-chip 12-bit / 4.096 GSPS analogue-to-digital converters (ADCs) and eight 14-bit / 6.554 GSPS digital-to-analogue converters (DACs), as well as field programmable gate array (FPGA) resources of 930,000 logic cells and 4,272 digital signal processing (DSP) slices. While this is sufficient data converter bandwidth for the readout of 8,000 MKIDs, with a 2 MHz channel-spacing, and a 1 MHz sampling rate (per channel), additional FPGA resources are needed to perform the DSP needed to process this large number of MKIDs. A solution to this problem is the new Xilinx RFSoC 2x2 board. This board costs only one fifth of the ZCU111 while still providing the same logic resources as the ZCU111, albeit with only a quarter of the data converter resources. Thus, using multiple RFSoC 2x2 boards would provide a better balance between FPGA resources and data converters, allowing the full utilization of the RF bandwidth provided by the data converters, while also lowering the cost per pixel value of the readout system, from approximately EUR2.50 per pixel with the ZCU111, to EUR1 per pixel.Comment: 7 pages, 6 figures. Presented at 19$^{th}$ International Workshop on Low Temperature Detectors, 21$^{st}$ July 2023. Resubmission to correct minor typo in author lis

Multimode simulations of a wide Field of View double-fourier far-infrared spatio-spectral interferometer

In the absence of 50 m class space-based observatories, sub-arc-second astronomy spanning the full far-infrared wavelength range will require space-based long-baseline interferometry. The long baselines of up to 10’s of meteres are necessary to achieve sub arcsecond resolution demanded by the science goals. Also, practical observing times command a field of view toward an arc minute or so, not achievable with a single on-axis coherent detector. This paper is concerned with an application of an end-to-end instrument simulator PyFIInS, developed as part of the FISICA project under funding from the European Commission’s 7th Framework Programme for Research and Technological Development (FP7). Predicted results of wide field of view spatio-spectral interferometry through simulations of a long-baseline, double-Fourier, far-infrared interferometer concept are presented and analysed. It is shown how such an interferometer, illuminated by a multimode detector can recover a large field of view at sub-arcsecond angular resolution, resulting in similar image quality as that achieved by illuminating the system with an array of coherent detectors. Through careful analysis, the importance of accounting for the correct number of higher-order optical modes is demonstrated, as well as accounting for both orthogonal polarisations. Given that it is very difficult to manufacture waveguide and feed structures at sub-mm wavelengths, the larger multimode design is recommended over the array of smaller single mode detectors. A brief note is provided in the conclusion of this paper, addressing a novel, more elegant solution to modelling far-infrared interferometers, which holds promise for improving the computational efficiency of the simulations presented here

Analysis and Optical Characterisation of Bolometric Integrating Cavities Including a Free Space Gap in the Waveguide Structure

Bolometric integrating cavities have been used with great success in previous far-infrared space missions, and are planned for extensive use in future missions where ever increasing sensitivity is required. It is critical for the purposes of design and the interpretation of results that these systems are thoroughly understood and optically characterised fully. Such systems, for manufacturing and mechanical reasons, may contain free space gaps between the feed horn antenna and the integrating cavity, and so it is necessary to include the effect of these waveguide openings in simulations. Since these pixels are electrically large, it is more feasible to model them by using the computationally efficient mode-matching approach. In this paper we discuss the elements required to model such pixels within the mode-matching approach and apply it to a typical pixel containing a free space gap, based on an experimental Transition Edge Sensor (TES) cavity waveguide pixel at SRON Groningen

Electromagnetic Techniques for Analysis and Design of Ultra Sensitive Receivers for Far-Infrared Astronomy

This thesis focuses on EM (electromagnetic) modelling methods for simulating the behaviour of receivers and detectors for far-IR (far-infrared) astronomy and CMB (cosmic microwave background) applications, toward an optimum design for SAFARI (the Spica Far-Infrared Instrument) on the proposed space based telescope SPICA (Space Infrared Telescope for Cosmology and Astrophysics). The computational methods required for modelling SAFARI-like receivers are described, and sophisticated conical waveguide mode matching theory is derived. Generic far-IR systems are investigated, including analysis of SAFARI-like multi-mode feed horns, and the absorber coupled superconducting TES (transition edge sensor) bolometers that are typically used in far-IR receivers. Special attention is given to the integrating cavity backshorts that serve to increase pixel efficiency, and new designs for improved cavity geometries, which provide high coupling between the detector and the incoming signal while reducing cavity losses and crosstalk, are presented. Where more than one simulation approach is employed for a particular problem, the agreement between the results served to mutually validate the approaches. Where necessary, experimental measurements were carried out for verification of the simulations, and the corresponding results are presented. The results of a measurement campaign carried out at SRON (Netherlands Institute for Space Research) during an extended visit during the summer of 2013 are presented, where a SAFARI-like horn antenna was characterised in terms of its frequency dependent throughput at THz (terahertz) frequencies. A series of cavity mounted absorber measurements are also described, where the detector components are appropriately scaled up in size to suit the frequency range of the in-house VNA (vector network analyser) system at NUIM (National University of Ireland, Maynooth). The main drivers for the work presented in this thesis were two Technology Research Programmes, both commissioned by ESA (European Space Agency)

Quasi-optical analysis of a far-infrared spatio-spectral space interferometer concept

FISICA (Far-Infrared Space Interferometer Critical Assessment) was a three year study of a far-infrared spatio-spectral double-Fourier interferometer concept. One of the aims of the FISICA study was to set-out a baseline optical design for such a system, and to use a model of the system to simulate realistic telescope beams for use with an end-to-end instrument simulator. This paper describes a two-telescope (and hub) baseline optical design that fulfils the requirements of the FISICA science case, while minimising the optical mass of the system. A number of different modelling techniques were required for the analysis: fast approximate simulation tools such as ray tracing and Gaussian beam methods were employed for initial analysis, with GRASP physical optics used for higher accuracy in the final analysis. Results are shown for the predicted far-field patterns of the telescope primary mirrors under illumination by smooth walled rectangular feed horns. Far-field patterns for both on-axis and off-axis detectors are presented and discussed

Progress in Spectral-Spatial interferometry at multi-THz frequencies - Potential applications

Spectral-spatial interferometry pioneered in a narrow band in the near infrared has not enjoyed much exploitation as a technique. Proposed as a promising modulation method for a potential Far-infrared future satellite, a period of study was performed on two testbeds to improve and evolve this technique in the laboratory in order to simplify some of the technical aspects and the data analysis involved. Here we will present an update on the successful upgrade of a previous wideband millimetric (0.3-1.0 THz) testbed to a far-IR (11-14THz) one, as well as the ongoing progress on a broadband setup for an imaging system with a commercial thermal-or mid-IR (8 to 12 micron or 25-35 THz) camera currently working as imaging FTS. Source size, coherence and technical issues are discussed

Analysis and Optical Characterisation of Bolometric Integrating Cavities Including a Free Space Gap in the Waveguide Structure

Bolometric integrating cavities have been used with great success in previous far-infrared space missions, and are planned for extensive use in future missions where ever increasing sensitivity is required. It is critical for the purposes of design and the interpretation of results that these systems are thoroughly understood and optically characterised fully. Such systems, for manufacturing and mechanical reasons, may contain free space gaps between the feed horn antenna and the integrating cavity, and so it is necessary to include the effect of these waveguide openings in simulations. Since these pixels are electrically large, it is more feasible to model them by using the computationally efficient mode-matching approach. In this paper we discuss the elements required to model such pixels within the mode-matching approach and apply it to a typical pixel containing a free space gap, based on an experimental Transition Edge Sensor (TES) cavity waveguide pixel at SRON Groningen

Analysis and Optical Characterisation of Bolometric Integrating Cavities Including a Free Space Gap in the Waveguide Structure

Bolometric integrating cavities have been used with great success in previous far-infrared space missions, and are planned for extensive use in future missions where ever increasing sensitivity is required. It is critical for the purposes of design and the interpretation of results that these systems are thoroughly understood and optically characterised fully. Such systems, for manufacturing and mechanical reasons, may contain free space gaps between the feed horn antenna and the integrating cavity, and so it is necessary to include the effect of these waveguide openings in simulations. Since these pixels are electrically large, it is more feasible to model them by using the computationally efficient mode-matching approach. In this paper we discuss the elements required to model such pixels within the mode-matching approach and apply it to a typical pixel containing a free space gap, based on an experimental Transition Edge Sensor (TES) cavity waveguide pixel at SRON Groningen