The Kingdom of Two Sicilies

We were recently in and around Naples. Inevitably you learn about local history, and not only Pompei and Herculaneum. And so you learn that in the first part of the 19th century, Naples was the capital of the Kingdom of Two Sicilies.

A quick look at the map will confirm two facts you probably already knew: Naples isn't in Sicily (either of them), and there is only one Sicily. So, why was there a Kingdom of Two Sicilies, and why was Naples the capital?

And thus begins a long descent into Wikipedia and Italian history - although Italy, as a country, didn't exist until 1861. Which, not by coincidence, was the end of the Kingdom, whose existence lasted just 34 years from 1816.

It all started in the year 999, when Norman pilgrims returning from Jerusalem happened to be staying with Prince Guaimar III in Salerno, south of Naples. While they were there, the city was attacked by Saracens. The Normans, who were made of tougher stuff than the locals, ridiculed and attacked the besiegers, in an episode reminiscent of John Cleese in Monty Python and the Holy Grail.

Yes, this is the same Normans who a few years later invaded England, winning the Battle of Hastings in 1066 and placing England under Norman control for the next couple of centuries. They were evidently a pretty convincing bunch in battle. It's a long way from Normandy to Sicily, but they got about a lot.

After their help to the Prince of Salerno, the Normans were welcome back any time. Comparing Sicily - lovely weather, great food - to Normandy, it's understandable that plenty of Normans fancied a visit to see for themselves. Mediterranean tourism is nothing new, even before Ryanair.

The history of the period immediately following is very confused. There were a lot of battles, during which the Normans gradually accumulated more power and territory. What is certain is that in 1061, Robert and Roger Guiscard took control of Sicily from a bunch of feuding fiefdoms. With Sicily as a base, they gradually moved the boundaries of their local empire eastwards and northwards. In 1077 they reached Naples and took control of it. In 1130, the Kingdom of Sicily was formally established with the blessing of Pope Innocent II. Its capital was Palermo, which is definitely in Sicily.

The Normans evidently got fed up with Sicily. In 1198 the throne passed to Frederick II of the House of Hohenstaufen. As you may guess, he wasn't Sicilian. Their base was in Swabia, their capital near present-day Stuttgart. They were in turn replaced by Charles I of Anjou in France in 1266.

Things came to a head in 1282, when the Sicilian population got fed up with all this remote rule and threw them all out in the War of the Sicilian Vespers (Lambrettas were still a few centuries away). The throne of Sicily passed to Frederick III of Barcelona. Remote working is nothing new.

It took a while for the dust to settle, at the Peace of Caltabelotta in 1302. The Kingdom of Sicily was divided into two parts, the island itself and the mainland part. But the subsequent naming was surreal. The island part became officially the Kingdom of Trinacria, though still generally referred to as the Kingdom of Sicily. The mainland part was officially called... the Kingdom of Sicily, though generally referred to as the Kingdom of Naples. Makes perfect sense, n'est-ce pas?

This odd state of affairs had a very long life. In 1759, the King of Sicily (meaning Naples not including Sicily) was Charles VII of the House of Bourbon, which is to say French. But then he got king-hunted, and decided to take the offered new job as King of Spain. That left a vacancy in Naples, which Charles filled with his son Ferdinand. One of Charles' last acts as King of Naples was to start the construction of the largest monument to megalomania in Europe, the Palace of Caserta, just north of Naples. The building itself is vast, with over 1200 rooms, while the Versailles-like garden stretches over 3 kilometres.

In 1799, Napoleon attacked Naples and briefly took control of it. Ferdinand was forced to flee to Sicily (the island), which was protected by the British under Nelson. Sicily was a British protectorate from 1806 to 1814, which I suspect not many people in Britain know.

In 1815 Napoleon was defeated and the British lost interest in Sicily. Ferdinand took control again. His stay on the island evidently hadn't endeared it to him, because he took the opportunity to wipe out the other Kingdom of Sicily and to take control of both of them. The resulting joint venture he renamed (as you may have guessed) the Kingdom of the Two Sicilies. The islanders understandably weren't keen on this and revolted, but this and subsequent rebellions were brutally suppressed by Ferdinand and again by his son, Ferdinand II with support from Austria.

The Kingdom of the Two Sicilies only had a short life, though. In 1860 Garibaldi, as the head of the new united country of Italy, attacked and conquered Sicily. In 1861, everything became part of the Kingdom of Italy. If you'd like to know more, I suggest starting with the Wikipedia article. You will soon find yourself drawn into the complete history, as I was.

Quantum Computing and Navigation - the State of the Art

I was fortunate to get tickets to the Economist's "Commercialising Quantum" conference on 13/14th May 2025. Over two days there were presentations and panels from people from manufacturers, researchers and other industry figures. Like all conferences, it was a bit of a mixed bag. But here are the main points that struck me.

When Will it be Useful?

Realistically, "quantum superiority" for a limited class of applications is probably 3-5 years away. IBM said 3, they're probably being optimistic though. "Q-Moore's Law" seems to hold - the number of qubits roughly doubles each year.

Strong consensus that the likely first application is chemistry and materials science (which is just a special case of chemistry anyway). For this you don't need anything spectacular, as soon as you have enough reliable ("logical") qubits to do more than conventional computers can (say 30-40), you have something you can use.

Error Correction

Raw physical qubits are extremely unreliable - error rates of 10^-2 or worse. To make it useful, you need very powerful error correction. Masses of effort in this right now. The problem is that first, it takes a lot of physical qubits to create a single usefully-reliable logical qubit, and second, error correction is (relatively) slow. That matters, because for some technologies you only have microseconds before the whole thing turns to mush due to decoherence.

People talked about "logical qubits" without saying what they meant in terms of physical per logical. You can build a logical qubit (lqubit) with nine physical qubits, but it won't get you anywhere close to the reliability you need. Current estimates are that it will take 100-1000 physical qubits to make one useful logical qubit. So if your problem needs 100 logical qubits, you need at least 10,000 physical qubits. It's worse than that. To achieve an overall say 10^-2 reliability, the reliability you need from each logical qubit increases with the number of them. So the number of physical qubits you need increases with the square of the complexity of the problem.

One company (Riverlane) has built an off-line error correction box, a 1U package using lots of FPGAs for speed. It sounds improbable, but they claim it works. You still have to program all the guard-bits in your quantum program, which is non-trivial, but they take care of the decoding.

How - Quantum Technologies

There are several competing raw physics approaches to building a quantum computer: superconducting, neutral atom, photonic, topological, trapped ion, quantum dot. There is a good survey article here . They all have been made to work at "toy" scale, and they all have $Bs of investment and serious companies (MS, Google, IBM, ...) behind them. They all have serious drawbacks, and none have been made to work at useful scale.

Clearly there will eventually be a winner, maybe two. I think it's fair to say that at this point nobody (who doesn't have a dog in the race) has the faintest idea which. It's not even certain that ANY of them can be made to work at scale, though given the $$$ and sheer number of quantum physics PhDs being thrown at them, something will probably emerge.

Crypto

THE talked-about QC application is cryptography, or rather breaking it. The nirvana is (relatively) rapid factorization of 2048-bit RSA public keys. It's still a long way off. Right now the estimate is that it will take about 10 million physical qubits. Assuming Q-Moore's Law, that is 15 years away. Supposing improvements in algorithms and error correction reduce that by a factor 10, call it 10 years. Still a long way off. (And "rapid" means in several hours, not seconds or microseconds).

Even so, there has been a lot of work on "post quantum cryptography" (PQC), i.e. cryptography which is resilient to attack using quantum techniques. NIST in the US has blessed several techniques. My guess is that the world will move fairly rapidly to using these, say within the next 3 years. That matters because for really critical stuff (like defence designs), state actors are already storing encrypted data hoping they'll be able to decode it "one day".

QC and AI

There were several sessions claiming to talk about this, but all the ones I attended were content free. Everyone agrees that QC will be part of the AI toolbox, but beyond that nobody had much to say.

Deployment

There were several companies proposing different kinds of "make QC usable for you" services and techniques. I'm 100% sure that this is the only way any "normal" software engineers will ever be able to use it, so this will be a big market. One day. 

Non-Computing Stuff - Quantum Navigation

Several sessions were about quantum-based navigation, i.e. getting GPS-like benefits without needing external radio signals. This is a huge deal because there are large parts of the world where GPS is unusable due to jamming and spoofing. There are two techniques, both dependent on fairly miraculous quantum technology. One is quantum INS - building accelerometers and gyroscopes that are orders of magnitude more stable than you get with classical techniques. The other is quantum gravimetry - measuring the local strength of the earth's magnetic field. Using that, you can relate your position to a map (which are available) and have a position accurate to within a few hundred metres.

The technology of quantum gravimetry is really mind-boggling, but a bit long to fit in the margin here. Basically it involves measuring the difference in position between two superposed quantum states of the same atom. If that seems reasonable to you, you have your head around quantum stuff a lot better than I do.