A recent technology quarterly about new quantum innovations, published in The Economist, referred to a disturbing development in quantum sensor technology:
Military types are interested, too. “You can’t shield gravity,” says David Delpy, who leads the Defence Scientific Advisory Council in Britain’s defence ministry. Improved gravity sensors would be able to spot moving masses under water, such as submarines or torpedoes, which could wipe out the deterrent effect of French and British nuclear submarines.
So much of the present nuclear balance of power (such as it is) depends on ballistic missile submarines being essentially invulnerable by virtue of being impossible to locate. Reportedly, almost no crew members about an American boomer (as subs carrying nuclear missiles are known) know the precise location of the ship, and nobody on land has the information.
If states suddenly feel their subs are vulnerable, it risks two big effects. First, it raises tensions in a crisis. If states fear they will lose their seaborne second strike capability, they may be inclined to launch a nuclear attack earlier. Second, if the safest leg of the nuclear triad (along with bombers and land-based missiles) suddenly seems vulnerable, it’s likely they will assemble and deploy more weapons in more locations, wasting money and raising the risk of accidental or unauthorized use.
As with other emerging nuclear-related technologies like hypersonic weapons, it would be better for everyone if we could agree to prohibit sensors that threaten subs. Alas, states are rarely so cooperative or trusting.