Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Scalable Quantum Logic Spectroscopy



Kaifeng Cui, Jose Valencia, Kevin Boyce, Ethan Clements, David Leibrandt, David Hume


In quantum logic spectroscopy (QLS), one species of trapped ion is used as a sensor to detect the state of an otherwise inaccessible ion species. This extends precision measurements to a broader class of atomic and molecular systems for applications like atomic clocks and tests of fundamental physics. Here, we develop a new technique based on a Schrödinger cat interferometer to address the problem of scaling QLS to larger ion numbers. We demonstrate the basic features of this method using various combinations of 25-Mg+ logic ions and 27-Al+ spectroscopy ions. We observe higher detection efficiency by increasing the number of 25-Mg+ ions. Applied to multiple 27-Al+, this method will improve the stability of high-accuracy optical clocks and could enable Heisenberg-limited QLS.
Physical Review Letters


quantum information, optical clocks, trapped ions, quantum metrology


Cui, K. , Valencia, J. , Boyce, K. , Clements, E. , Leibrandt, D. and Hume, D. (2022), Scalable Quantum Logic Spectroscopy, Physical Review Letters, [online],, (Accessed March 4, 2024)
Created November 2, 2022, Updated January 8, 2024