Decoherence happens at the loss of superposition and the resulting either/or. Before that a quantum calculation performs in parallel every possible value that the register can represent

Using superposition for computation requires avoiding decoherence for as long as possible. This has proved difficult and is still the limiting factor in the size and power of a quantum computer. Various physical and chemical means for building and connecting qubits have increased the number of qubits possible to connect before decoherence collapses the calculation, but

Quantum computers are restricted to calculations that can be performed faster than decoherence occurs in the superposed wave functions. For over a century this restricted time for a quantum computing operation to less than ten seconds

Qubes are room-temperature quantum computers with thirty qubits, the decoherence boundary limit for circuit-connected qubits, combined with a petaflop-speed classical computer to stabilize operations and provide a database. The most powerful qubes are theoretically capable of calculating the movements of all the atoms in the sun and its solar system out to the edge of the solar wind

Qubes are only faster than classical computers when they can exploit quantum parallelism. At multiplication they are no faster. But in factoring there is a difference: to factor a thousand-digit number would take a classical computer ten million billion billion years (lifetime of universe, 13.7 billion years); using Shor’s algorithm, a qube takes around twenty minutes

Grover’s algorithm means that a yearlong search using a classical computer in a random walk of a billion searches a second would take a qube in its quantum walk 185 searches

Shor’s algorithm, Grover’s algorithm, Perelman’s algorithm, Sikorski’s algorithm, Ngyuen’s algorithm, Wang’s algorithm, Wang’s other algorithm, the Cambridge algorithm, the Livermore algorithm,

entanglement is also susceptible to decoherence. Physical linkage of quantum circuits is necessary to forestall decoherence to useful time frames. Premature or undesired decoherence sets a limit on how powerful qubes can become, but the limit is high

it has proved easier to manipulate superposition than entanglement for computing purposes, and therein lies the explanation of many

The quantum database is effectively distributed over a multitude of universes

the two polarized particles decohere simultaneously no matter the physical distance between them, meaning the information jump can exceed the speed of light. The effect was confirmed by experiment in the late twentieth century. Any device that uses this phenomenon to communicate messages is called an ansible, and these devices have been constructed, but undesired decoherence has meant the maximum distance between ansibles has been nine centimeters, and this only when both were cooled to one millionth of a K above absolute zero. Physical limitations strongly suggest further progress will be asymptotic at best

powerful but isolated and discrete, somewhat like brains

questions of Penrose quantum effects in the brain have been effectively rendered moot, as these also occur in qubes by definition. If both structures are quantum computers, and one of them we are quite certain has consciousness, who is to say what’s going on in the other

human brain operations have a maximum theoretical speed of 10 ¹⁶operations per second

computers have become billions to trillions times faster than human brains. So it comes down to programming; what are the operations actually doing

hierarchical levels of thought, generalization, mood, affect, will

super-recursive algorithms, hypercomputation, supertasks, trial-and-error predicates, inductive inference machines, evolutionary computers, fuzzy computation, transrecursive operators,

if you program a purpose into a computer program, does that constitute its will? Does it have free will, if a programmer programmed its purpose? Is that programming any different from the way we are programmed by our genes and brains? Is a programmed will a servile will? Is human will a servile will? And is not the servile will the home and source of all feelings of defilement, infection, transgression, and rage?

could a quantum computer program itself?

WAHRAM AND SWAN AND GENETTE

Wahram saw Swan emerge from the lock door, looking around for him, and when she saw him, he waved, and then she did too, her expression pinched, he thought, her head tilted to the side. She looked at him in quick glances—she didn’t know how he would be. Suddenly he remembered that in the actual flesh she was a big bag of problems. He nodded a little deeper than he would have normally, trying to reassure her, and then thought that that might not be enough, and extended both hands, realizing as he did so that he was already back in a different world, Swancentric and intense. She threw herself on him in a rush, and he felt sure it looked like he was hugging back, or had even invited the hug.

Jean Genette emerged from the lock and stood looking up at them, and Wahram greeted him with another bow.

“So you want to find one of the hanging ships?” he said.

They did. Apparently it might have something to do with the attack on Terminator. So Wahram led them across the spaceport to the gate for the railgun launcher angled to send ferries into polar orbits around Saturn. These orbits were popular for viewing the rings and the hexagonal storm at Saturn’s south pole. Wahram had already gotten permission from the authorities to take a cloud diver into the upper reaches of the planet; probably the council was happy to have him involved, as the Saturnian liaison to the incursion.

They took off with only a pilot and crew aboard with them, and after they were cast toward the north pole, Swan and the inspector told Wahram what they had been doing since they’d left Mercury. Wahram, feeling uneasy that he could not fully reciprocate and tell them about his activities, given the council’s orders, compensated by asking them a lot of questions about the investigation and its results so far. These turned out to be very interesting, even disturbing, and Wahram pondered to the point of a certain distraction the idea that there might be someone out there killing whole terraria. That the investigation had reduced their likeliest suspect pool to the population of Earth did not strike him as remarkable progress. All trouble comes from Earth, as the saying had it.

The cloud diver was not a big ship, and though it was very fast, the trip still took long enough for Swan to begin to exhibit the signs of distress and antsiness he remembered so well. Then happily they were above Saturn’s north pole, looking down at the dark side of the rings, as it was the northern winter. From behind the sun the rings were peach in tone, the circumferential scoring so finely etched and yet so vast that one could not help being a bit taken aback. Even on their dark side the rings were far brighter than the nightside of the planet, making for an aura or halo effect of eldritch beauty, all framing the deep blue of Saturn’s winter north.