Circuit Quantum Electrodynamics

Objectives: Initialize, manipulate, and read out the quantum state of a superconducting circuit.
Benefits: Integrating the signal generation and detection improves synchronization and simplifies setup.
Relevant products: UHFLI Lock-in Amplifier, UHF-AWG Arbitrary Waveform Generator, UHF-DIG Digitizer, UHF-MF Multi-frequency option
Additional resources: Superconducting Qubit Characterization
Active Reset of Superconducting Qubits

Circuit quantum electrodynamics (cQED) aims at speeding up numerical computation by using on-chip superconducting resonant circuits (so-called quantum bits, qubits). For cQED experiments the UHF hardware offers arbitrary signal generation with advanced modulation features for quadrature (I/Q) pulse generation as well as digital homodyne detection at an unprecedented speed.

The two phases of a typical cQED experiment are performed with the following tools:

  • Qubit control (preparation and gate operations): The UHF-AWG generates arbitrary dual-channel I/Q modulation pulses with independent envelope and carrier control
  • Qubit readout: The UHFLI with the UHF-DIG Digitizer enables pulsed qubit readout with 30 ns time constant and large data throughput

All tools are fully integrated into the LabOne user interface and support easy integration into LabVIEW, Python, and Matlab. Internal cross-domain triggering simplifies the synchronization of preparation and measurement phase, and open the possibility to perform ultra-fast feed-forward protocols for deterministic qubit reset and quantum error correction.

Circuit QED Setup

The qubit chip is mounted inside a cryostat. Signals sent to and from the qubit are in the microwave domain (5-10 GHz). The UHFLI generates and analyzes the signals in the baseband 0-600 MHz. Up- and downconversion is achieved with analog mixers.

Key features of the UHFLI Lock-in Amplifier for this application

  • UHF-AWG amplitude modulation for generation of intermediate-frequency I/Q channel pulses
  • 30 ns demodulation time constant
  • Cross-domain triggering between UHF-AWG and UHF-DIG for sequence branching
  • segmented memory and fast data streaming with UHF-DIG

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