Quantum Pen

The Project

Quantum Pen is a handheld device about the size of a pen. It projects real interference and diffraction patterns onto any flat surface — no dark room, no setup, no software needed. With swappable modules (650 nm red, 450 nm blue, and a diffraction grating), one single device demonstrates three distinct quantum optics phenomena. Students can directly measure fringe spacing with a ruler and see how changing wavelength affects the pattern, turning an abstract equation into a hands-on experience. A high school physics class. The teacher explained the double-slit experiment using whiteboard sketches and textbook diagrams. Everyone nodded along. But no one actually saw what interference looks like. The real lab equipment costs over $1,000 and needs a completely dark room. That gap — between understanding the math and seeing the real phenomenon — inspired the team to build a device that puts the experiment directly into a student's hand. Several challenges came up. Our first slit was hand-cut from razor blades — the fringes showed up, but the rough edges made the pattern uneven. We switched to photo-etched metal foil for clean edges. The module swapping mechanism didn't align consistently at first; several test users couldn't get the module to click in on the first try. We redesigned it with a spring-loaded latch and chamfered guide, so the module self-centers as it slides in. The blue laser modules also had inconsistent power — some were too dim to see in a lit classroom. We switched suppliers and added an incoming inspection step to test each diode before assembly.

View this project on YouTube