August 8, 2022

Gaining quantum control from loss

Gaining quantum control from loss

Researchers at the Hong Kong University of Science and Technology (HKUST) have demonstrated a new way to control the quantum state through the loss of particle. This process is usually avoided in the quantum devicesThis approach is offering a new way towards the realization of unprecedented quantum states.

Manipulating a quantum system requires a subtle control of quantum state with zero imperfect operations, otherwise the useful information encoded in the quantum states is scrambled.  Loss of particles that consist of the system is a common issue which has long been seen as an enemy of quantum control and was avoided through the isolation of the system.

The idea of non-Hermitian physics with loss has been actively examined in classical systems, but such counter-intuitive phenomena were only recently realized and observed in genuine quantum systems. In the study, HKUST researchers adjusted the systems’ parameters such that they sweep out a closed loop around a special point—also known as an exceptional point occurring in the non-Hermitian system.  It was discovered that the direction of the loop (i.e. whether it goes clockwise or anti-clockwise) determines the final quantum state.

Another implication of the findings is how two seemingly unrelated mechanisms: non-Hermitian physics (induced by loss) and spin-orbit coupling, interplay. (

The paper was published in Nature Physics.

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