Functional Overview

This chapter provides the overview of the features provided by the QHub Instrument. The first section contains the description of the graphical overview and the hardware and software feature list. The next section section details the front panel and the back panel of the instrument. The last section provides product selection and ordering support.

Features

Figure 1: QHub instrument functional diagram

The QHub Instrument according to Figure 1 consists of several internal units (light blue color) surrounded by several interface units (dark blue color) and the back panel on the right-hand side. The orange blocks are optional units that can be either ordered at the beginning or upgraded later. The arrows between the panels and the interface units indicate selected physical connections and the data flow.

The Zurich Instruments QHub enables scalable quantum processor control through automated synchronization and low-latency communication between all components of a Quantum Computing Control System (QCCS). It provides high-level software access to powerful real-time capabilities designed for the most pervasive use cases in quantum computing.

With 56 ZSync ports, the QHub supports systems with up to 448 microwave control, readout, or flux control channels for precisely timed and stable gate and readout operations. Central data processing enables feedback methods that require global information of the system state, e.g. for quantum error correction. Including all signal processing, the feedback latency is below 550 ns between any connected instruments.

Decoding algorithms can be efficiently implemented on a powerful FPGA core using a ready processing infrastructure accessible in Python. Optional direct programming of the FPGA provides the flexibility required in developing novel decoder algorithms.

Software Features

• LabOneQ Python framework for high-level multi-instrument control and experiment definition and execution
• Web-based, high-speed user interface for multi-instrument control and monitoring

Front Panel Tour

The front panel Control LEDs are arranged as shown in Figure 2 and listed in Table 1.

Figure 2: QHub Quantum System Hub instrument front panel

Table 1: QHub Instrument front panel description

Position	Label / Name	Description
A	ZSync	56 ZSync port synchronization LEDs. Shows the status of the corresponding ZSync port link off No instrument has been detected. white An instrument has been detected, but no connection is established yet blue Link with the instrument is established yellow Busy, establishing a connection red Error, connection not successfully established. The error can be clock, receiver or transmitter related
B	-	Air inlet (important: keep clear from obstruction)
C	multicolor LEDs	off Instrument off or uninitialized blink all LEDs blink for 5 seconds → indicator used by the Identify Device functionality
		Ext Ref	off External Reference Signal not present/detected blue External Reference Signal is present and locked on to yellow External Reference Signal present, but not locked on to red External Reference Signal present, but lock failed
		Status	off Instrument off or uninitialized blue Instrument is initialized and has no warnings or errors yellow Instrument has warnings red Instrument has errors
D	Soft power button	Power button with incorporated status LED off Instrument off and disconnected from mains power blue flashing rapidly (>1/sec): Firmware is starting flashing slow (<1/sec): Firmware ready, waiting for connection constant: Instrument ready and active connection over USB or Ethernet red breathing: Instrument off but connected to mains power → safe to power off using the rear panel switch, or restart using the soft power button flashing: Instrument booting up constant: Fatal error occurred

Back Panel Tour

The back panel is the main interface for power, control, service and connectivity to other ZI instruments. Please refer to Figure 3 and Table 2 for the detailed description of the items.

Figure 3: QHub Quantum System Hub instrument back panel

Table 2: QHub Instrument back panel description

Position	Label / Name	Description
A	AC 100 - 240 V	Power inlet, fuse holder, and power switch
B	Earth ground	4 mm banana jack connector for earth ground, electrically connected to the chassis and the earth pin of the power inlet
C	Trigger In	Digital trigger input
D	Trigger Out	Digital trigger output
E	External Clock In 10 MHz	External Reference Clock Input (10 MHz) for synchronization with other instruments
F	External Clock Out Sysref	External Reference Clock Input (Slow reference, sysref) for synchronization with other instruments
G	External Clock Out 100 MHz	External Reference Clock Input (100 MHz) for synchronization with other instruments
H	LAN 1 GbE	1 Gbit LAN connector for connection to the host computer
I	USB	Universal Serial Bus (USB) 3.0 port connector. Only for maintenance operations.
J	JTAG	Connector for programming and debugging the FPGA
K	ZSync	Inter-instrument synchronization and real-time feedback connector - attention: this is not an Ethernet plug, connection to an Ethernet network might damage the instrument.
L	-	Air outlet (important: keep clear from obstruction)

Ordering Guide

Table 3 provides an overview of the available QHub products and options. Upgradeable features are options that can be purchased anytime without the need to send the Instrument back to Zurich Instruments.

Table 3: QHub Instrument product codes for ordering

Product code	Product name	Description	Field upgrade possible
QHUB56	QHub56 Quantum System Hub	Base instrument with 56 ZSync ports	-