That gold, chandelier-like structure you see in photos of quantum computers is not the computer itself. It’s a massive refrigerator. The actual quantum processor is a tiny chip, roughly the size of a fingernail, mounted at the very bottom of that structure. Everything else exists for one reason: to keep that chip colder than outer space.
The Chip Needs Extreme Cold
Most quantum computers built by major labs use superconducting qubits, which only work at temperatures around 15 millikelvin. That’s 0.015 degrees above absolute zero, roughly 200 times colder than the void of deep space. At these temperatures, electrical resistance vanishes and quantum effects become stable enough to perform calculations. Any warmer, and the delicate quantum states collapse into useless noise within nanoseconds.
Getting to that temperature is the hard part. No single cooling method can jump from room temperature to near absolute zero. Instead, the system cools in stages, each one bringing the temperature down further. That’s what creates the layered, tiered look.
Why It Looks Like an Upside-Down Wedding Cake
The structure is called a dilution refrigerator, and it’s built as a series of circular metal plates stacked vertically, each one smaller and colder than the one above it. Fermilab describes the layout as resembling “an upside-down wedding cake,” with around seven plates of decreasing diameter suspended from each other. The top plate sits near room temperature. The bottom plate, where the quantum chip lives, sits at millikelvin temperatures.
Each plate represents a thermal stage. The upper stages use conventional cooling techniques to drop from room temperature down to a few degrees above absolute zero. The lower stages use a process involving two forms of helium (helium-3 and helium-4) that mix together in a way that absorbs heat, pulling temperatures down to that final 15 millikelvin range. The plates are physically separated so heat from one stage doesn’t leak into the next.
Why There Are So Many Cables
The dense tangle of gold-colored wires running between the plates is one of the most visually striking parts, and also one of the biggest engineering headaches. Each qubit needs its own dedicated control and readout lines. Unlike classical processors, where billions of transistors share a relatively small number of data pathways, quantum processors require wiring that scales linearly with the number of qubits. A 100-qubit machine needs hundreds of individual high-bandwidth coaxial cables running from room-temperature electronics all the way down to the chip at the bottom.
These cables carry microwave pulses that manipulate and read the qubits. But each cable is also a potential highway for heat to travel down into the coldest stages. So the wiring passes through attenuators and filters at each plate, which weaken stray signals and bleed off heat before it can reach the processor. On the output side, the faint signals coming back from the qubits pass through amplifiers so sensitive they need to operate at cryogenic temperatures themselves. All of this signal conditioning hardware hangs from the plates, adding to the chandelier’s visual complexity.
This wiring problem is a major bottleneck for scaling quantum computers. Researchers are exploring alternatives, including replacing coaxial cables with optical fibers. One team recently demonstrated qubit readout using a single optical fiber for input and one for output, which could dramatically reduce the physical bulk inside future machines.
The Gold Color Is Functional
The gold appearance comes from actual gold plating on many of the copper components. Gold is an excellent thermal conductor and doesn’t oxidize, which matters when you need heat to flow predictably between surfaces at cryogenic temperatures. The plates and mounting hardware are typically made from oxygen-free, high-conductivity copper, chosen because it transfers heat efficiently and contains fewer impurities that could trap residual warmth at ultra-low temperatures.
What You Don’t See in Photos
The iconic chandelier photos show the refrigerator with its outer shells removed. During actual operation, the entire structure is enclosed in a series of nested cylindrical cans, like a set of nesting dolls. These vacuum-sealed shells serve multiple purposes: they maintain the vacuum that prevents air molecules from carrying heat inward, and they block electromagnetic interference that would scramble the qubits. Researchers at the University of Oregon, for instance, use bespoke shields machined from oxygen-free copper, with additional off-the-shelf magnetic shielding layered around the outside.
When fully assembled and running, a quantum computer looks far less dramatic. It resembles a large white or gray cylinder, sometimes the size of a closet, with conventional cables running out to racks of room-temperature electronics. The chandelier only makes an appearance when engineers open it up for maintenance or to swap in a new processor chip.
Why Not Just Make It Smaller?
The quantum chip itself is tiny. The refrigerator is enormous because the laws of thermodynamics demand it. Removing heat from something that cold requires moving it through multiple stages, each with its own hardware, plumbing, and wiring infrastructure. The dilution refrigerator also needs a continuous supply of helium mixtures circulating through specialized pumps and heat exchangers, all of which take up space.
As quantum computers scale to thousands or millions of qubits, this becomes a real problem. More qubits mean more cables, more cooling power, and larger refrigerators. Fermilab is building the world’s largest dilution refrigerator, called Colossus, specifically to address the cooling demands of next-generation quantum hardware. The engineering challenge of quantum computing isn’t just building better qubits. It’s building a refrigerator big enough to keep them all cold while routing hundreds or thousands of signal lines to each one without letting any heat sneak in.