UK’s first Quan­tum-Safe Long-Distance Com­mu­ni­ca­ti­on

Quan­tum Com­mu­ni­ca­ti­on offers uni­que secu­ri­ty advan­ta­ges com­pared to clas­si­cal tele­com­mu­ni­ca­ti­ons solu­ti­ons: it is immu­ne to future cyber­at­tacks — even tho­se from Quan­tum Com­pu­ters, which, once ful­ly deve­lo­ped, will have the poten­ti­al to break the stron­gest cryp­to­gra­phic methods curr­ent­ly in use within a very short time. For this reason, the deve­lo­p­ment and deploy­ment of Quan­tum Com­mu­ni­ca­ti­on Net­works is incre­asing­ly beco­ming the focus of rese­arch.

Rese­arch teams from the Uni­ver­si­ties of Bris­tol and Cam­bridge have suc­cessful­ly demons­tra­ted quan­tum-secu­re data trans­mis­si­on over long distances for the first time — inclu­ding a quan­tum-encrypt­ed live video call. A fiber optic net­work was used that inte­gra­tes two quan­tum key dis­tri­bu­ti­on (QKD) methods into an exis­ting fiber optic infra­struc­tu­re: On the one hand, unbre­aka­ble encryp­ti­on keys embedded in par­tic­les of light were used. On the other hand, ent­an­gle­ment dis­tri­bu­ti­on was employ­ed, in which two Quan­tum Par­tic­les are intrin­si­cal­ly lin­ked regard­less of their distance. The net­work con­sists of two metro­po­li­tan Quan­tum Net­works in Bris­tol and Cam­bridge, con­nec­ted via a back­bone of four long-distance opti­cal fiber links span­ning 410 kilo­me­ters and three inter­me­dia­te nodes. It uses sin­gle-mode fiber from the EPSRC Natio­nal Dark Fib­re Faci­li­ty and low-loss opti­cal swit­ches. This is the first time that a long-distance net­work with dif­fe­rent quan­tum-safe tech­no­lo­gies — inclu­ding ent­an­gle­ment dis­tri­bu­ti­on — has been suc­cessful­ly demons­tra­ted. The results were pre­sen­ted at the Opti­cal Fiber Com­mu­ni­ca­ti­ons Con­fe­rence (OFC) in San Fran­cis­co in March 2025.

The expe­ri­ment marks the first suc­cessful inte­gra­ti­on of mul­ti­ple quan­tum-safe tech­no­lo­gies in a long-distance net­work and demons­tra­tes the poten­ti­al of Quan­tum Net­works that com­bi­ne dif­fe­rent quan­tum-safe approa­ches with clas­si­cal com­mu­ni­ca­ti­on infra­struc­tu­re. It was car­ri­ed out using the UK’s Quan­tum Net­work (UKQN), which has been estab­lished over the last ten years with fun­ding from the Engi­nee­ring and Phy­si­cal Sci­en­ces Rese­arch Coun­cil (EPSRC) and as part of the Quan­tum Com­mu­ni­ca­ti­ons Hub. The team will pur­sue this work through the new­ly fun­ded EPSRC pro­ject, the Inte­gra­ted Quan­tum Net­works Hub. Its visi­on is to estab­lish Quan­tum Net­works at all distance sca­les: from the local net­wor­king of Quan­tum Pro­ces­sors to natio­nal-sca­le ent­an­gle­ment net­works for quan­tum-safe com­mu­ni­ca­ti­on, dis­tri­bu­ted com­pu­ting and sens­ing, to inter­con­ti­nen­tal net­wor­king via low-earth orbit satel­li­tes. This is expec­ted to lay the foun­da­ti­on for future, far-rea­ching Quan­tum Net­works.