In this paper, we introduce the work on hardware and software built to manage the optical bench which hosts the optical squeezer source at the Virgo site in Cascina. In the past, the ex-perimental setup implemented frequency-independent squeezing and it will be soon recon gured in order to implement frequency-dependent squeezing via EPR entanglement for Virgo gravitational-wave detector. Furthermore we introduce an idea of automation for this prototypic subsystem in order to deliver a compact and robust apparatus which does not require surveillance of an operator

Alberto Gennai

Catherine Nguyen

Diego Passuello

Ettore Majorana

Fiodor Sorrentino

Imran Khan

Jean-Pierre Zendri

Luca Naticchioni

Marco Vardaro

Martina De Laurentis

Mateusz Bawaj

Sibilla Di Pace

Valeria Sequino

In this paper, we introduce the work on hardware and software built to manage the optical bench which hosts the optical squeezer source at the Virgo site in Cascina. In the past, the ex- perimental setup implemented frequency-independent squeezing and it will be soon recongured in order to implement frequency-dependent squeezing via EPR entanglement for Virgo gravitational- wave detector. Furthermore we introduce an idea of automation for this prototypic subsystem in order to deliver a compact and robust apparatus which does not require surveillance of an operator

Bawaj, Mateusz

De Laurentis, Martina

Di Pace, Sibilla

Gennai, Alberto

Khan, Imran

Majorana, Ettore

Naticchioni, Luca

Nguyen, Catherine

Passuello, Diego

Sequino, Valeria

Sorrentino, Fiodor

Vardaro, Marco

Zendri, Jean-Pierre

ZENODO

Electronic hardware and software development for the Advanced Virgo EPR squeezer

Archivio della ricerca- Università di Roma La Sapienza

2nd GRavitational-waves Science & technology Symposium (GRASS 2019), Padova, ITElectronic hardware and software developmentfor the Advanced Virgo EPR squeezerMateusz Bawaj1, Martina De Laurentis2, Sibilla Di Pace3,4, Alberto Gennai5, Imran Khan6,7,Ettore Majorana4, Luca Naticchioni4, Catherine Nguyen8, Diego Passuello5,Valeria Sequino9, Fiodor Sorrentino9, Marco Vardaro10 and Jean-Pierre Zendri111 INFN, Sezione di Perugia, I-06123 Perugia, Italy2 Università di Napoli “Federico II”, Complesso Universitario di Monte S.Angelo,I-80126 Napoli, and INFN Sezione di Napoli, Italy3 Università di Roma “La Sapienza”, I-00185 Roma,Italy4 INFN Sezione di Roma, I-00185 Roma, Italy5 INFN Sezione di Pisa, I-16146 Pisa, Italy6 INFN Sezione di Roma Tor Vergata, Italy7 Gran Sasso Science Institute, I-67100 L’Aquila, Italy8 APC, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris,Sorbonne Paris Cité, F-75205 Paris Cedex 13, France9 INFN Sezione di Genova, I-16146 Genova, Italy10 Università di Padova, Dipartimento di Fisica e Astronomia, I-35131 Padova,and INFN Sezione di Padova, Italy11 INFN Laboratori Nazionali di Legnaro, I-35020 Legnaro, Italymateusz.bawaj@pg.infn.itMarch 19, 2020AbstractIn this paper, we introduce the work on hardware and software built to manage the opticalbench which hosts the optical squeezer source at the Virgo site in Cascina. In the past, the ex-perimental setup implemented frequency-independent squeezing and it will be soon reconfigured inorder to implement frequency-dependent squeezing via EPR entanglement for Virgo gravitational-wave detector. Furthermore we introduce an idea of automation for this prototypic subsystem inorder to deliver a compact and robust apparatus which does not require surveillance of an operator.DOI: 10.5281/zenodo.35543621 IntroductionQuantum Noise (QN) is a phenomenon which gives high contribution to the overall noise in the ad-vanced interferometric Gravitational-Wave Detectors (GWDs). In the previous interferometer genera-tion, the most relevant QN component was dominating in the high frequency region (300 Hz–10 kHz) ofthe detection band. This component of noise was attenuated by injection of optimal vacuum squeezedstate [1]. In fact, Virgo Scientific Collaboration has already implemented Frequency-Independent2nd GRavitational-waves Science & technology Symposium (GRASS 2019), Padova, ITSqueezing (FIS) injection to the readout port of Advanced Virgo and reported improvement of thesensitivity curve of around 3 dB [2]. Currently, the Collaboration focuses on the work on the Frequency-Dependent Squeezing (FDS) injection using a Filter Cavity (FC) which will reduce QN either in thehigh and low frequency range. At the same time, Virgo Squeezing working group is studying a possiblealternative way of producing frequency–dependent squeezed states without the use of FC. The mecha-nism of FDS without filter cavity, called Einstein–Podolsky–Rosen (EPR) squeezing, was theoreticallyproposed by Ma et al. [3] and subsequently demonstrated feasible by scientific group from ANU andHamburg using a proof-of-principle setup [4]. At the moment, development facility for the productionof squeezed vacuum at EGO/Virgo site is being adapted for the preliminary experiment on the EPR.This task is carried by the INFN group from Naples and Genova in collaboration with APC. Theexperiment represents a first step toward implementation of the new squeezing generation technique.For the purpose of the project, INFN group from Perugia together with groups from Pisa, Padovaand Rome have been developing various types of photo-detectors and software based on Finite-StateMachines (FSMs). In this paper, we overview the current state of work on the facility and we sum-marize in details the tasks related to the development of electronics and software for implementationof EPR squeezer. In particular, we focus on the engineering of analogue electronics for cavity lockingand squeezed state measurement. We conclude by explaining the near future steps: FSM applicationscheme, noise hunting and operator independent lock acquisition.There are three main motivations for this work. In principle the setup must be as accessibleas possible to scientists from various fields of expertise. Thus, its handling must not require anycomplex operation on the feedback controls, like tuning or calibration. This approach is a first stepto minimize necessary human interaction with the subsystem and can be obtained by its automation.Accurate automation will also help us in accomplishing the second goal which is the maximizationof the subsystem Quality of Service (QoS). Last but not least, we want to reach the low noisecharacteristics and keep the subsystem compatible with Virgo infrastructure. We describe below thesystem developed using custom built devices and various devices built for Virgo.2 EPR squeezer design assumptionsFrom the optical design of the EPR squeezer shown in Figure 1, we inferred the control system designrequirements. In total, we need fourteen feedback loops of various kind: two Optical Phase-LockedLoops (OPLLs) to lock lasers in frequency; two locking loops for non-linear crystal cavities and four forMode-Cleaner (MC) cavities longitudinal lock, implementing Pound–Drever–Hall technique (PDH);one Proportional–Integral–Derivative controller (PID) for Mach–Zehnder interferometer for light in-tensity stabilization, two PIDs for Coherent Control (CC) loop for squeezing phase stabilization [5]and yet another three for temperature control loops for non-linear crystals and etalon. Several of thesedevices need to be fed with a reference frequency. For this purpose we use a custom made 14-channel,synchronous Direct Digital Synthesis (DDS) generator. Actuation on the cavity mirrors is done usinghigh-voltage piezoelectric actuators. We use a custom built amplifier to drive them. In the next twoparagraphs we describe the hardware and the software structure of the system.2nd GRavitational-waves Science & technology Symposium (GRASS 2019), Padova, ITAOMAOMgAOMAOMAOMAOMIdler AUXLaser 4 2MainLaser424 2Signal AUXLaserPLL 1PLL 2Mach–ZehnderTEST CAVITYMCGIdler MCSignal MCSHGOPOETALONSignalhomodyneIdlerhomodynetrans.PDHPDHPDHPDHPDHPDHtrans.EOM EOMFigure 1: Generic scheme of the optical design in the EPR experiment with locking and automation de-tails. In the figure are indicated optical cavities with corresponding photo-detectors for locking, OPLLphoto-detectors, electro-optic modulators for PDH sidebands generation and homodyne detectors forconditional squeezing detection.3 Hardware system architectureHardware architecture of the electronic system, controlling the optical bench, is shown in Figure 2.For better understanding, the scheme should be read from the left to the right and from the top tothe bottom. Symbols in the left column depict optical cavity longitudinal lock, while symbols on theright depict OPLL components. Fast demodulated photo-diode is shared between the two chains sinceit provides signal for both. The loops are implemented using analogue and mixed-signal devices. Thelatter: DDS, Digital Signal Processing (DSP) card, OPLL board and temperature PID are managedby a Personal Computer (PC) via digital links.In the system, there is one reference frequency source synchronizing all DDS channels. Sine formsgenerated by the DDS are used to: drive Electro-Optic Modulators (EOMs) and demodulate signalfrom the corresponding photo-detectors in the PDH loops; give reference frequency for phase detectorsin the OPLL and in the CC loops.Beneath we report improvements introduced in the electronic equipment. In order to provide areliable reference frequency for the system, we built a PLL stabilized Voltage-Controlled Oscillator(VCO) based reference clock source using ADF4360-7 development board. Configuration of the VCOgenerator is handled by a micro-controller which monitors constantly the PLL-lock status and reacts incase of failure. Moreover, the micro-controller uses its own watchdog to further increase the reliabilityof the running firmware.High voltage drivers used to drive piezoelectric actuators in optical cavities are linear amplifiers.2nd GRavitational-waves Science & technology Symposium (GRASS 2019), Padova, ITDSP cardFast demodulated photo-diodeHigh-voltage driverReference clock sourceDDS generatorOptical PLLOptical cavity actuatorLaserSlow photo-diodePCElectric analogue linkElectric digital linkTemperature PID controllerFigure 2: Hardware architecture scheme shows devices in the system and physical links between them.Single reference clock source feeds synchronous, multi-channel DDS generator. Loop implementingPDH technique is shown schematically on the left. In this loop two photo-detectors, indicated as slowand demodulated, are involved. Signals coming from the detectors are digitalized and processed on theDSP card which provides a correct, frequency dependent gain. Correction signal is then sent to thehigh-voltage driver and to the piezoelectric actuator. Optical PLL is depicted on the right. This loopuses direct output from the fast photo-detector and sends it to the OPLL board which implementsanalogue filter for laser’s piezo and digital PID controller for laser’s temperature. In the figure electriclinks are indicated by arrows, its colour indicates the type of connection while arrowhead indicates thedirection of information flow. Symbol placed inside a pile symbol depicts that there are many devicesof the kind in the system.We introduced internal reference voltage modification to lower their output noise. We suppressedpower line noise by introducing a high-voltage stabilizer in the power supply. The use of the stabilizerlet us decrease filtering capacity and at the same time maintain the output voltage pulsation low.After the upgrade we obtained power supply output noise Eout = 3 µV/√Hz at the corner frequency200 Hz measured with 30 mA on resistive load. Amplifier’s output noise is now VRMS = 4.85 µV in theoperation bandwidth from 1 Hz to 20 kHz.Existing fast photo-detectors, which implement on-board demodulation, were redesigned to providesignals with differential outputs. It makes them robust against the noise induced in wires connectingthe optical bench with 19′′ racks. We used an existing Virgo Data AcQuisition (DAQ) interconnectionelectric standard. Input preamplifier of the photo-detector was reviewed and its bandwidth wasincreased to 80 MHz when using 0.5 mm diameter photo-diode and 120 MHz for 0.3 mm diameter.Changes concern also the homodyne detector. We introduced modifications to the electronic circuit2nd GRavitational-waves Science & technology Symposium (GRASS 2019), Padova, ITdesign and we improved mechanical stability. Both lead to better noise characteristics and robustnessof operation. We measured 82 dB of Common-Mode Rejection Ratio (CMRR) at 270 Hz.Lock acquisition stability was improved by software modification and automation. This argumentis a topic of the next section.4 Software system architectureBefore describing the software improvements, lets have a closer look on the Information Technol-ogy (IT) architecture shown in Figure 3. In this figure all devices shown in the dashed frame areconfigurable by software. At present, several of them are configured via Tango server [6] while othersare individually interfaced with a PC. Considering that Tango is supported by Virgo infrastructurethis is a temporary state. Eventually all devices will be configured via Tango server. The main advan-tages of using Tango server is its compatibility with Virgo and the possibility of simultaneous work ofscientist on various sections of the optical bench.Ethernet· ¸ ¹ º » ¼ ½ ¾ º ¿ ÀDSPcardÉDDS v2generatorTemperaturePID controllerOpticalPLLDDS v1generatorPCDataAcquisitionOptical linkEthernetUSBUSBUSBEth19-inch rackRemoteusersTANGO SERVERPythoninterfaceFigure 3: Software architecture scheme. In the scheme, electronic devices are shown in the dashedrectangle. Outside of the rectangle there is IT infrastructure. Digital connections are depicted asarrows.Software in the system is divided in two categories; firmware and PC software. Firmware ispresent in each configurable device but we will briefly describe only the firmware of the DSP cardas it is the most interesting from the point of view of automation. We use DSP accelerated DAQsystem designed for processing digitalized analogue signals for controls of the super attenuator. TheDAQ is a distributed system composed of rack crates and relative servers. Crates are connected toTango, firmware distribution system and time distribution system for synchronization. Each cratecan host up to twelve DSP cards. Each DSP card, takes input signals from on-board Analog-to-2nd GRavitational-waves Science & technology Symposium (GRASS 2019), Padova, ITDigital Converters (ADCs) or from other boards placed in the same crate via back panel. Signalsare processed by a dedicated piece of code (firmware) compiled by a custom Software DevelopmentKit (SDK). Output of the firmware calculation can be sent either to the on-board Digital-to-AnalogConverters (DACs) or to any other card inside the crate. SDK supports math operations and easesdesign of digital filters. The newest version of the SDK supports implementation of FSMs.We exploit the natively supported digital filters and FSMs in the firmware which we wrote inorder to lock automatically feedback loops. In the system, we can distinguish loops between; loops foroptical cavities which use PDH technique and loops for Mach–Zehnder (MZ) and CC which use PIDcontroller. FSM implementation differs in both cases but both of them gives the same functionality:when initialized the FSM calibrates itself and after the calibration it can be controlled by the state ofone variable. The value determines a desired state of the cavity that the FSM will attempt to reachby autonomous operations.5 ConclusionsIn this paper, we reported necessary upgrades in the electronic system managing the Virgo R&Dsqueezer. We introduced to the system a robust reference clock oscillator, we lowered the noise of thehigh-voltage section and we modified the fast photo-detectors to make them electrically compatiblewith Virgo standards. Finally, we improved the homodyne detector stability. Currently, we arestudying a new architecture of software in order to increase automation by governing FSMs by externalsoftware from a PC. In the near future, we will duplicate our devices to satisfy the requirements of theEPR optical layout. Implementation of the EPR requires extension of the FSM logic on the additionalhardware. Further, we will commission the new software and perform measurements of the QoS.References[1] Caves CM. Quantum-mechanical noise in an interferometer. Physical Review D [Internet]. American PhysicalSociety (APS); 1981 Apr 15;23(8):1693708. Available from: http://dx.doi.org/10.1103/physrevd.23.1693[2] Virgo and AEI collaborations. Increasing the astrophysical reach of Advanced Virgo via the application ofsqueezed vacuum states of light. Physical Review Letters. American Physical Society (APS); forthcoming2019[3] Ma Y, Miao H, Pang BH, Evans M, Zhao C, Harms J, et al. Proposal for gravitational-wave detection beyondthe standard quantum limit through EPR entanglement. Nature Physics [Internet]. Springer Science andBusiness Media LLC; 2017 May 15;13(8):77680. Available from: http://dx.doi.org/10.1038/nphys4118[4] Gniesmer J, Korobko M, Steinlecher S, Schnabel R. Frequency-dependent squeezed states for gravitational-wave detection through EPR entanglement. Quantum Information and Measurement (QIM) V: QuantumTechnologies [Internet]. OSA; 2019; Available from: http://dx.doi.org/10.1364/qim.2019.s2b.4[5] Chelkowski S, Vahlbruch H, Danzmann K, Schnabel R. Coherent control of broadband vacuum squeezing.Physical Review A [Internet]. American Physical Society (APS); 2007 Apr 23;75(4). Available from: http://dx.doi.org/10.1103/physreva.75.043814[6] Tango Community. Tango software documentation. Available from: https://tango-controls.readthedocs.io/en/latest/

English

Electronic hardware and software development for the Advanced Virgo EPR squeezer

Abstract

Similar works

Full text

Available Versions

ZENODO

Archivio della ricerca- Università di Roma La Sapienza