[Homemade Quantum Computer NMRQCP] "FID (Free Induction Decay) signal", which is the biggest climax of this project! 🎉
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 have some incredibly exciting news to share. We have finally succeeded in real-time observation of the "FID (Free Induction Decay) signal", which is the biggest climax of this project! 🎉
I will introduce the decisive moment when the equipment built from scratch with collected parts all worked together to capture the invisible movements of quanta!
Listening to the Voices of Atoms! What is an "FID Signal"?
What exactly is an "FID signal" in the first place?
After aligning the direction of hydrogen nuclei (protons) in water by applying a strong magnetic field (large current), we suddenly turn off the switch. Then, the protons are pulled by the Earth's magnetic field and return to their original state while spinning around like a wobbling top (precession).
The "extremely faint radio waves" emitted by the atoms as they return are the FID signal. To use an analogy, it's like the lingering reverberation that gradually fades away with a ringing sound after striking a bell hard.
This is the Quantum Waveform! A Historic Moment
Now, please take a look at the actual waveform captured by my homemade system!
💡 Explanation of the Graphs
[Top: Time Domain] Immediately following the noise right after the current is cut off, you can confirm a waveform that draws a smooth curve while decaying towards zero—the very shape of "an FID!".
[Bottom: Frequency (FFT)] When this wave is decomposed by frequency, a clear and sharp peak appeared right around "2.04kHz"!
This "2.04kHz" is super important. Actually, this perfectly matches the frequency at which hydrogen nuclei react (Larmor frequency) under the strength of Japan's geomagnetic field!
In other words, this is not just random noise or a machine malfunction; it is absolute proof that I was able to visualize the "interaction between the Earth's magnetic field and quanta" using a circuit I built with my own hands.
The Homemade Hardware That Supported the Experiment
It took so many parts and so much trial and error to get this far. Here is the equipment that finally worked together as a system this time.
- Coil: Homemade (PVC pipe + 1600 hand-wound turns of 2UEW 0.5mm enamel wire)
- Amplifier: Ultra-low distortion, ultra-low noise op-amp AD797BRZ (the heart of the system that survived that smoke incident!)
- Power Supply: 12V fully sealed lead-acid battery (for high polarization current) + 9V rectangular alkaline battery (to drive the amp)
- Controller: M5Stack CoreS3 + Mini Relay Unit for M5Stack
- Input to PC: 96KHz / 24-bit Hi-Fi USB Audio Interface
The Next Challenge: "The Battle Against Noise"
With this, the initial goal of creating "one from zero" has been achieved!
However, the joy is fleeting. The current waveform is still heavily affected by environmental noise (hum noise and switching noise). From now on, we will transition to a "tuning phase" to increase the purity of this entire system.
By transitioning from a breadboard to a universal board, shielding with an aluminum case, replacing with BNC cables, and thoroughly cutting low-frequency noise using a high-pass filter with metallized polyester film capacitors, I will further train the hardware to draw out an even cleaner sine wave!
This is the first step in building the foundation for quantum computer development. Please continue to support the project!
- 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!
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