[Homemade Quantum Computer NMRQCP] The Absolutely Unmistakable Timing of "Polarization" and "Receiving"

*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 introduce the "timing switching" that is the cornerstone of hardware control for the quantum computer, along with the program I actually wrote and how the testing went!

The Absolutely Unmistakable Timing of "Polarization" and "Receiving"

In EFNMR, there is a "Polarization" phase where a strong current is passed through a coil to align the protons (hydrogen nuclei) in the water perpendicular to the Earth's magnetic field.

However, immediately after that, we must move to the "Receiving" phase to pick up the extremely faint "FID signal". If you do these two at the same time, a massive current will flow into the delicate receiving circuit, charring the parts in an instant (a lesson learned from the past op-amp burnout incident).

Creating "Automatic Switching" with M5Stack and a Relay

Therefore, I created a mechanism to safely and automatically repeat these two states. What I use is a small microcontroller "M5Stack CoreS3 Lite" and a "Mini Relay Unit for M5Stack".

Using the Arduino IDE as the development environment and utilizing a library called M5Unified, I wrote a basic state machine program.

// --- 1. Polarization Phase ---
digitalWrite(RELAY_PIN, LOW); // Relay OFF
M5.Display.println("1. Polarizing...");
M5.Display.println("Relay: OFF (Charge)");
delay(5000); // Polarize for 5 seconds

// --- 2. Receiving Phase ---
digitalWrite(RELAY_PIN, HIGH); // Relay ON
M5.Display.println("2. Receiving...");
M5.Display.println("Relay: ON (Listen)");
delay(3000); // Receive signal for 3 seconds

The movement is very simple. First, the relay is turned OFF, and a large current flows through the coil for 5 seconds to polarize it. Next, the relay is turned ON to physically cut off the current from the coil, switching to the operational amplifier (receiving circuit) side for 3 seconds to wait for the signal.

Actual Operation Test

Here is a photo when I actually ran it.

The relay unit is connected to the Grove port (Pin 8) of the M5Stack, and the text on the screen is set to green to display the current status. In the photo, you can see that the "2. Receiving..." and "Relay: ON (Listen)" phase is currently being executed.

Hearing the physical clicking sound of the relay and seeing the phases automatically switch every few seconds, I'm moved to feel, "The system is really alive!" With this, the heart of the system for safely running experiments without destroying the hardware is complete.

• 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!