Documentation
Quantum@Home demonstrates small, home-scale physics experiments. It uses off-the-shelf, low-cost detectors that provide live data related to quantum events. The detectors are connected to the web server in Bladel, the Netherlands.
Available experiments
Natural radiation
The Natural Radiation page receives detection counts from a GQ GMC-300S Geiger counter, which uses a Geiger-Müller tube for detection. When ionizing radiation interacts with the gas in the tube, it can eject an electron from a gas atom. The resulting ionization triggers an avalanche of further ionizations and produces the electrical pulse recorded as a detection.
Live detections
The Live detections chart shows the most recent 60 one-second samples. A low baseline marker represents a recorded zero. A taller bar represents one or more detections during that second, and values above one are printed above the bar.
Detection history
The first row shows counts this minute, counts this hour, and counts today.
A value marked partial has incomplete live-detector coverage for that local period. The number is the count actually recorded; it is not an estimate of what the missing interval might have contained.
The second row shows average counts per day, week, and month:
- the daily average uses only completed earlier local days;
- the weekly average uses only completed Monday-through-Sunday weeks;
- the monthly average uses only completed calendar months.
A day qualifies as complete when at least 99% of its expected one-second live samples were received. Weeks and months qualify only when every included day is complete. Current and incomplete periods are excluded from these averages.
The long-term chart offers three views:
- the last 30 local days, with one bar per day;
- the last 26 local weeks, with one bar per Monday-through-Sunday week;
- the last 52 local weeks, with one bar per Monday-through-Sunday week.
A partial bar shows the subtotal that was actually recorded. A subdued baseline marker means no numeric measurement is available for that period. Recorded zero and unavailable data are therefore not treated as the same thing. Weekly partial totals include the recorded days that are available, without estimating missing days.
Counts per minute distribution
The distribution chart uses complete one-minute intervals from the retained live-detector history. Each bar shows the percentage of complete minutes containing a particular number of detections. The line shows the Poisson distribution expected from the observed mean count rate.
A Poisson distribution is expected when detections occur independently at an approximately steady average rate. Short data sets fluctuate visibly; the observed bars should generally approach the expected curve as more complete minutes accumulate. Partial minutes, unavailable periods, simulated data, and daily summary records are excluded.
About the detector
When the detector is live, the page shows its location, source status, model, firmware, detector type, and the manufacturer-documented safe range. The displayed range of 0–50 counts per minute corresponds to 72,000 counts per day. This manufacturer figure is contextual information for this detector; it is not a general medical or environmental safety assessment.
If the physical detector is not available, hardware-specific values are shown as unavailable.
Quantum randomness
The Quantum Randomness page contains a timed distribution experiment designed for random bytes produced by a Crypta Labs Cicada 0.5 USB quantum random number generator.
A byte can have any integer value from 0 through 255. If the QRNG output is uniform, every value has the same expected frequency:
1 / 256 = 0.390625%, displayed on the chart as approximately 0.391%.
Running an experiment
Select a duration of 0.1, 1, 10, 30, or 60 seconds and press Start. While the experiment is running, the chart updates with only the bytes processed during that run. Press Stop to finish early. After completion or stopping, the final chart and summary values remain visible until another run begins.
The six summary boxes show:
- the selected duration;
- elapsed time;
- bytes processed;
- the arithmetic mean of the byte values;
- the standard deviation of the 256 observed percentages around the expected percentage;
- experiment status.
For a perfectly uniform byte stream, the expected mean is 127.5. The displayed standard deviation summarizes the spread of the 256 observed bin percentages around 0.390625%. It is shown as an absolute percentage difference; technically, that difference is measured in percentage points.
Distribution chart
The chart contains one bar for each possible byte value from 0 through 255. The dashed reference line marks the expected uniform frequency of approximately 0.391% per value.
Short experiments naturally show larger irregularities because they contain fewer bytes. As more bytes are processed, the distribution should usually become more even, although a genuinely random result is never required to look perfectly uniform.
Pointing to a bar shows its byte value, count, and percentage. Bars that exceed the fixed visible chart range are clipped at the top, but their underlying values and tooltips remain unchanged.
What is quantum here?
Inside the QRNG, a controlled light source emits photons toward a sensor. Even when the average light level is steady, the exact number of photons emitted and detected during each very short sampling interval fluctuates unpredictably. This photon shot noise arises from the quantum nature of light: individual photon-emission and detection events have probabilities, but their precise outcomes cannot be predicted.
The sensor converts those fluctuations into an electrical signal, which is digitized into raw values. The device checks that the measured noise remains dominated by the quantum process rather than by ordinary electronic or environmental noise. The raw data is then conditioned to remove bias and produce a uniform stream of random bits. Conditioning does not create the randomness; the quantum measurement process remains its source.
The resulting bits are sent to the computer through USB and combined into the byte values shown in the experiment.
About the QRNG
The page shows the QRNG location, device status, model, firmware, quantum source, and output rate.
Device status refers exclusively to the physical QRNG hardware. It shows Connected only when that device is actually detected and connected; otherwise it shows Disconnected. It does not change merely because an experiment starts or stops.
When the physical device is connected, the quantum source is photon shot noise and the specified output rate is 500 kb/s. Hardware-specific values that are not available are displayed accordingly.
Schrödinger’s cat
The Schrödinger’s Cat page uses quantum random data from the Crypta Labs Cicada 0.5 USB QRNG to simulate the radioactive decay of a single rubidium-82 nucleus.
What you are seeing
The box contains a virtual cat and a simulated radioactive device that releases poisonous gas if the nucleus decays. Rubidium-82 has a half-life of approximately 75 seconds. While the box remains closed, the display shows the changing probabilities of the cat being alive or dead. After 75 seconds, the box opens automatically and reveals one of those outcomes.
A half-life of 75 seconds means that a rubidium-82 nucleus has a 50% probability of decaying during that interval. It does not mean that every nucleus decays after exactly 75 seconds. The decay time of an individual nucleus is unpredictable, and shorter decay times are more likely than longer ones.
What is quantum here?
Schrödinger’s cat is a thought experiment proposed in 1935 to expose the strange consequences of extending quantum mechanics from microscopic systems to everyday objects. In the idealized setup, a cat is sealed in a box with a radioactive nucleus, a detector, and a mechanism that releases poison if the nucleus decays. Before measurement, quantum theory describes the nucleus as a superposition of decayed and undecayed states. Because the detector, poison mechanism, and cat are linked to that event, the complete system is described as entangled with it until the box is opened and an outcome is observed.
This website does not create a macroscopic quantum superposition. Instead, the QRNG supplies random data generated from photon shot noise, a genuinely quantum physical process. The software converts that data into a simulated decay time following the same exponential probability law as radioactive decay. If the simulated nucleus decays before the box opens, the cat dies; otherwise, it remains alive. The physical quantum randomness is real, while the rubidium-82 nucleus, decay, poison mechanism, and cat are simulated.
About the experiment
The page shows the experiment location and type, the randomness source, the QRNG’s quantum source, the simulated nucleus, its half-life, and how the decay time is obtained. In absence of actual radioactive material, the decay time is simulated from the physical quantum randomness supplied by the QRNG.
Time and persistence
Calendar totals and chart periods use Europe/Amsterdam local time. Internally, minute timestamps may remain in UTC so that measurements stay unambiguous during daylight-saving-time transitions.
Live natural-radiation history is stored across application restarts. A sudden interruption can lose a small amount of the newest unsaved data, and any resulting gap is reflected by a partial period rather than by an estimated replacement.
Quantum randomness experiment results are not stored as long-term history. A completed chart remains on the page for the current browser session until another run begins or the page is reloaded.
Schrödinger’s cat outcomes are simulation results rather than detector history and are not included in the Natural Radiation records.
Language support
The site supports English, Dutch, German, and Spanish. The language switch in the header cycles through those languages and keeps the visitor on the same page whenever possible.
Help pages
Documentation, Glossary, About, Privacy Policy, and Terms of Use are served through the shared Help navigation. The Markdown content is loaded per language, while the surrounding layout remains shared.