[Homemade Quantum Computer NMRQCP] The "1600-Turn Hand-Wound Coil"

*Original Japanese version is available here.

 Hello! I'm a KOSEN student taking on the challenge of developing a quantum computer using a homemade Earth's Field NMR (EFNMR) system.

This time, I'll be sharing the production of the sensor coil, which can be called the "heart" of the quantum computer, and a high-current energization test using the circuit I built previously! It's a record of some pretty grueling physical labor (lol).

An Endless Path of 250 Meters... The "1600-Turn Hand-Wound Coil"

In EFNMR, a giant coil is required to apply a magnetic field to the target water (protons).

First, to make the bobbin (core), I cut a transparent PVC pipe with an outer diameter of 48mm using an SK11 pipe cutter. Then, I continuously wound 0.5mm 2UEW enamel wire around it.

To secure the necessary magnetic field strength and inductance, the number of turns is a whopping 1600 turns, which translates to a wire length of about 250 meters!

3 Tips for a Successful Hand-Wound Coil (Notes of Blood and Sweat)

I spent several days winding it by hand, and this task truly required perseverance. For anyone else who might make a hand-wound coil in the future (is there anyone?), I'm leaving some notes based on my failures.

• Secure it temporarily with tape: If your hand slips halfway through and the wire sags or loosens, you'll have to start all over again and fall into despair. Securing it firmly with tape at regular intervals is an ironclad rule.
• Absolutely do it with 2 people: It's definitely better to split the work between two people: one holding and turning the PVC pipe, and the other holding the enamel wire taut. There's a limit to what you can do alone.
• Take appropriate breaks: Because you have to constantly keep the wire pulled tightly so it doesn't slacken, your hands get unusually tired. I proceeded while taking regular breaks.

The Fateful Power-On Test! Will the Surge Protection Diode Win?

With the coil completed, I connected it to the MOSFET drive circuit I implemented the other day and conducted a high-current energization test simulating the actual polarization phase.

To completely prevent noise contamination from the commercial power supply, I used a fully sealed lead-acid battery (12V12Ah WP12-12) for the main power, and controlled the ON/OFF of the "N-ch power MOSFET 2SK4017(Q)" with pulses from the M5Stack.

My biggest concern was the "intense back electromotive force (surge)" generated when the current to the coil, which has massive inductance, is cut off. I was nervously sweating over whether this would destroy the MOSFET... but the result was a huge success!

Thanks to the "Fast Recovery Diode 20NFA40" I had mounted on the board functioning perfectly as a freewheeling diode, I was able to confirm that the MOSFET could switch safely and accurately without breaking.

To the Next Step

With this, the basic operation of the hardware and power circuit has been proven!

Next, at last, I will set a sample bottle filled with high-purity purified water (deionized water) inside this coil. By linking the M5Stack's pulse control with the USB sound card capture, I will move on to an experiment that really feels like a quantum computer: "the actual measurement and FFT analysis of proton precession (FID signal)".

• Daily experiment notes and code: Available on my GitHub repository (nmr-qc-project)
  
• Real-time development scenes and oscilloscope waveforms: Posting on X (formerly Twitter)
  

If you are wondering things like "Will it really work?" or "How do you generate waveforms?", please bookmark this blog and follow me on X!