QD lite

Quantum-Demonstrator-Lite

A Plug and play Quantum Algorithm Demonstrator for Students. Integrates into QuBeads, a software for visualising up to three Qubits, with fully customisable Quantum Gates.

Picture of the Setup used at the Max Planck Institute of Quantum Optics

The Quantum Demonstrator Lite can be used to demonstrate algorithms up to three Qubits over seven positions, and these can be viewed in Detail with the QuBeads Software, available at https://spindrops.org/2.5.0-beta1/download.html (We recommend going with the Beta, as it has the updated visualisation)

NOTE: The final product is to be used with QuBeads, the successor to SpinDrops. The auto Update is not available in SpinDrops but is on the ToDo for QuBeads.

The Quantum Demontrator Lite utilises 21 RC522 readers to maximise flexibility with the Quantum gates, allowing you to create your own custom gates. These are being controlled by a Raspberry Pi Pico2 Microcontroller, which in turn communicates with the PC over USB.

It was designed to be somewhat affordable to institutions and Schools, with a price around 400€ depending of the suppliers you choose, and the means of assembly.

Getting Started

For anybody wanting to build the Demonstrator, you should have a few prerequisite Tools:

Note: Should you decide to assemble the PCB yourself, be aware the SMD components are not the easiest to work with. A revamped version is a WIP which will drastically reduce the amount of components needed

Electronics

|Electronics/ contains the PCB Schematic and Board design. The PCB was designed in KiCad. Parts needed for the PCB can be found via the Schematics, the BOM or here.

Main PCB (Current state)

The current State is functional, but a simpler V2 is being worked on.

The Main PCB contains the Raspberry Pi Pico and all the power conversion needed to power the NFC readers, the LEDs and the Pi Pico itself.

For a complete PCB assembbly service, you can expect to pay ~85€

Parts 1, 8, 11, 12 and 19 will have to be hand soldered. Numbers 8, 9 and 12 are Normal THT components, 19 has to be wired and then soldered. The Raspberry Pi Pico2 has an Unusual way of soldering it to the PCB, due to the assumption one doesn't have a hotplate available.

Top Side	Bottom Side
	Marked by the red Arrow are two through Holes, these must be kept unfilled, double check this when ordering the PCB

First solder down two of the SMD Pads of the Pi Pico, then turn the board around and fill the Marked through holes with solder, make sure to keep it warm for a bit, and probe the PCB for connection between the USB and the data pins on the Pi Pico.

Connecting PCBs

The Quantum Demonstrator uses three almost identical PCBs to connect the individual NFC Readers to the Main PCB. These Connecting PCBs also mount the LEDs for the illumination. While all of the Connecting PCBs are the same, the Placement of the connectors is different for one of the three boards. These connectors are labeled with A.1, A.2 and B.1, B.2. This is neccessary due to cabeling and space saving.

Two Boards must be configured with the A.1 and A.2 ports soldered and one Board with the B.1 and B.2 ports

For all three Connection PCB, you will need:

Miscelaneous Parts

Important Note for the NFC readers: These must be the JoyIT readers, as the pinout is not compatible between different vendors. The ones we specify have to have straight Through hole connectors, you can desolder the included conneectors or order via JoyIT directly and ask to have these connectors omitted, such that you can solder your own.

Mechanical Construction

The Case for the Quantum Demonstrator is Mostly 3D Printed, with two extra Aluminium Extrusions for stability.

Rccommended Print settings:

Bill of Materials

BOM of Assembly 1, List of Parts to 3D print marked in Red (🔴)

Todo: Link Parts in here to parts in Project On the Prusa XL this would need 4-5 Printbeds

Assembly of the Case

Heatset Inserts

In preperation for assembly, insert the threaded Heatset Inserts into the pre made holes. For this set your soldering iron to aroun 250°C and slowly but firmly melt and press the insert into the hole. Try to keep it as level as possible to the Surface. The Following pcitures show where to position the Inserts.

Top Side	Bottom Side

Connection to the Aluminium Extrusion

There are multiple screwholes from the outside accessing the Aluminium extrusion. Insert the Matching screw, at a T-Nut onto it, and slide it onto the Aluminium Extrusion. Start with the Shoulder Sections, then do the middle section, then the Feet to tie it all to gether. Only put the lid on right at the end.

Mounting of PCBs

The Connection PCBs are screwed down with three M4 Screws, while the Main PCB is screwed down with three M2 screws.

Installing LEDs

Glue the LED strip down on the marked region. Make sure the Pinout is correct, adn solder it to the given Pads. To aid in diffusion a Thin plastic sheet is glued to the back of the Lid pieced to coder the Lighting slits (A piece of paper also works).

Software

The Quantum Demonstrator requires some Embedded and some PC side software.

Prerequisites

Embedded Software

Flash the C++ Program main.cpp onto the Raspberry Pi Pico 2 via USB.

PC Side Software

Download the PC_side_Software/ folder and run

python main.py          

Quick check without hardware or GUI:

python selftest.py

For a more in depth explaination: /PC_side_Software/README.md

Constructing the Quantum Gates

Download the desired Gates from /CAD files/Quantum Gates/ and 3D print them. Then glue An NFC Tag into each Indent (on single Qubit gates only one, on Mulit Qubit gates two or even three)

Using the Quantum Demonstrator (Work in Progress)

Connect the Demonstrator to 12V power and USB, and Turn it on Start python main.py and select the USB device in the dropdown Menu, and check if you can see Gates appear when you place them on the readers. "The Autowrite Json" automatically writes the JSON ever time an update is registered. This means you can continously import these files into spindrops.The directroy it deposits the files in can be chosen on launch. Now Start spindrops and import the newly generated QD_output.json File. Congratulations! You now have a functioning Quantum Demonstrator.

Enrolling New Gates into the Database (Heavy Work in Progress)

Run python enroll.py --port /dev/ttyACM0 and then follow the instructions. The Names are only Important if you want to designate your own gates via the spin drops Syntax.

Known Issues / ToDo

When enrolling gates the UUID gets entered incorrectly. Fix: Use multiple reads and verify against each other - Temporary fix, reenroll the gate.

ToDo

• Add GUI to the enroll process
• Fix framing issues in gui.py
• Package as Binary
• Proper spindrops integration -> WIP

Revamped PCB (HEAVY WIP)

to lower the costs of single piece production move from custom designed Voltage conversion to premade TRACOS.

Staged Design 12V -> 5V -> 3.3? vs Drirect Design 12V -> 5V and 12V -> 3.3V